WI Pisonian Conspiracy Succeeds (2023 ed)

[John Fredrick Parker]

What if the senatorial conspiracy to kill Nero and raise Gaius Calpurnius Piso to become Emperor had succeeded? Some discussion so far:

Gaius Calpurnius Piso seems to have been a decent enough man (although not without some issues, but few upper class Romans didn't) and had his conspiracy against Nero been successful, may have averted the civil war following the latter's death. Among his associates were Seneca and the poet Lucan, so certainly his rule could see a lot of cultural achievements. His son Galerianus may also have been a decent ruler by virtue of being wise enough to not stick his neck out into the chaos of the civil war after Nero.

His relative Licinianus also seems to have been a very good candidate for emperor...

Cnaeus Domitius Corbulo, surely would have been a better emperor than Nero. As one of the few Roman generals, he was able to successfully fight against the Parthians. He was an extremely capable man, not only in the military sense.

I was thinking this myself, the man would have made an able emperor, may not have been the youngest, so say the piso conspiracy works and Corbulo is placed on the throne, he may only rule for 10 years but could have been a good 10 years and seeing as how he has only daughters, either he adopts someone else to become his hier or he names a son in law/grandson hier. To boot his daughters were also distant descendants of Augustus.

You know, if the conspiracy to kill Nero and put Gaius Calpurnius Piso on the throne succeeds, I can see him being under a lot of pressure (similar to Nerva OTL) to name an heir who's popular with the people and army; Corbulo would certainly fit the bill there. As to Corbulo's successor in turn, he had a couple of daughters by the time of his OTL death, so I'm guessing he'd be looking for a prospective son-in-law who could continue the new dynasty; if he succeeds, you've got three successive capable emperors.

Now that I mention this -- Corbulo's eldest daughter is already married to Annius Vinicianus (another anti-Nero conspirator who was killed OTL, lives TTL), and likely has been for some time by 65 CE; that said, his younger daughter, Domita Longina, might already be married here, but she's still very young and wouldn't have been for long. (OTL the latter eventually married Domitian, but that's likely averted here.)

Revisiting this -- it seems whenever the Pisonian Conspiracy was discussed on the board previously, the general consensus was "you get an earlier civil war". But when you look at who was actually in command of legions and where in 65 CE (as opposed to 68 CE), you find the context is a bit different -- sure, you still have Galba and Otho commanding forces in Spain, but the ever popular Corbulo is still commanding in Syria, while (the Julio-Claudian psudo-connected) Vespasian is still in Africa, and Germania Inferior is commanded by the son of one of Caligula's victims (and who OTL would become one of Nero's victims in 67 CE). Unlike OTL's 69 CE, Vespasian is not in so strong a position to make his own play, and the legions of both Spain and Gaul/Germania are commanded by men who are unlikely to aggressively throw their hat in the ring against the Senate aligned new dynasty as Vitellius was OTL (though that doesn't mean they won't make a move if they sense an opportunity).

So if there's sentiment in the Roman Army looking to oppose "Nero's usurper", they'd probably lean toward pinning their hopes on Corbulo; likewise, if Corbulo is made the new imperial heir, then likely none of the legions (save maybe Vespasian's) will have any real objections to the new dynasty. So I'd say it comes down to him, which also likewise means the Judean Revolt also becomes a factor in this.

So building off of this -- let's say Piso is made emperor, and he names Corbulo as his heir (partly to secure the legions); and maybe Corbel's heir, in turn, can be Vinicianus (or maybe an alternative son-in-law). How do you think these reigns would fare, compared to OTL's Emperors of 69 CE and the Flavian Dynasty? How is history altered?

---CONSOLIDATION---

So I realize the AH prospect of "restoring the Republic in Rome after the reigns of Augustus and Tiberius" is usually an idea that gets laughed out of the room, including in these parts, but... well, look at the scenario I gave above: you have the Senate killing an Emperor and (perhaps partly due to a lack of potential male relatives) promoting one of their own leaders to be the new Emperor; then you have that new "senatorial emperor" securing the support of the military by naming the most accomplished and popular general alive at the time to be his successor (a Trajan to his Nerva, if you will); and as it happens, this general-emperor-to-be has only daughters, and his son in law happens to be the son of a man who attempted to lead a "republican" revolt a few years eaelier (Vinicianus' dad happens to be a figure in Caligula's assassination, and subsequently was the guy who convinced Scibonianus to revolt against Claudius).

Looking at these three men, and I just can't help but see a move to restore power to the Senate, and a move toward restoring "Roman Popular Politics" as the driving force of government (basically, the kind of politicking that traditionally linked the senatorial class to the Roman people, kind-of-sort-of what was done in the Late Republic), as opposed to competing for the emperor's favor. And I think they might actually have a shot of making it stick -- after all, Augustus has long since solved the issue of how you keep the army loyal to the state as an institution instead of to their local commanders and/or governors (basically, by creating a payment system that takes up a majority of the imperial budget), and the Praetorian Guard, for all the issues it raised with the imperial system OTL, had indeed done wonders for negating any threat of political violence returning to the bad levels it got to when the republic was in it's later stages. I mean yeah, this kind of stability may only last for as long as Rome's rulers don't actively f*** things up, but TTL you've got them starting off on a pretty strong foot, with figures like Seneca still alive to offer their guidance.

Am I crazy here? Do the Pisonian Conspirators have an actual shot at "Restoring the Republic" in the scenario where they pull off their plot?

 

[kholieken]

Restoring Republic is impossible without restoring great families and multiple imperium holders to restraint each other. Killing Emperor would only result in succession of dictator. Sulla and Marius had proven that power is now too concentrated and Senate can be ignored by ambitious man.

 

[John Fredrick Parker]

Sulla and Marius had proven that power is now too concentrated and Senate can be ignored by ambitious man.

Yeah, but there's a reason the likes of Sulla grew to become such a threat after the Marian Military Reforms -- when legions depend on the generosity of their commanders to get the benefits and severance pay, they're obviously going to become more loyal to their military commanders than they are to the state/republic; this is a large part of why Rome was so goddam unstable during the Late Republic. And a big reason for why the subsequent Empire was so stable for so long is because of the reforms of Augustus, not least of which was buckling down and creating a pension program for the Roman Army, and then spending basically as much money as required to make sure said program was well funded (which is how the military became the Roman Empire's dominant expense by far).

My point above -- once these reforms are implemented, and once the state has gotten used to implementing them, just how necessary is the position of "Roman Emperor" as such to keep the system running? And my point wasn't "kill Nero, Republic is restored", so much as it was looking at the men likely to subsequently become emperor thereafter, and asking "Could or would Republican institutions regain their strength with such men at the helm?"

 

[Mildtryth]

---CONSOLIDATION---

So I realize the AH prospect of "restoring the Republic in Rome after the reigns of Augustus and Tiberius" is usually an idea that gets laughed out of the room, including in these parts, but... well, look at the scenario I gave above: you have the Senate killing an Emperor and (perhaps partly due to a lack of potential male relatives) promoting one of their own leaders to be the new Emperor; then you have that new "senatorial emperor" securing the support of the military by naming the most accomplished and popular general alive at the time to be his successor (a Trajan to his Nerva, if you will); and as it happens, this general-emperor-to-be has only daughters, and his son in law happens to be the son of a man who attempted to lead a "republican" revolt a few years eaelier (Vinicianus' dad happens to be a figure in Caligula's assassination, and subsequently was the guy who convinced Scibonianus to revolt against Claudius).

Looking at these three men, and I just can't help but see a move to restore power to the Senate, and a move toward restoring "Roman Popular Politics" as the driving force of government (basically, the kind of politicking that traditionally linked the senatorial class to the Roman people, kind-of-sort-of what was done in the Late Republic), as opposed to competing for the emperor's favor. And I think they might actually have a shot of making it stick -- after all, Augustus has long since solved the issue of how you keep the army loyal to the state as an institution instead of to their local commanders and/or governors (basically, by creating a payment system that takes up a majority of the imperial budget), and the Praetorian Guard, for all the issues it raised with the imperial system OTL, had indeed done wonders for negating any threat of political violence returning to the bad levels it got to when the republic was in it's later stages. I mean yeah, this kind of stability may only last for as long as Rome's rulers don't actively f*** things up, but TTL you've got them starting off on a pretty strong foot, with figures like Seneca still alive to offer their guidance.

Am I crazy here? Do the Pisonian Conspirators have an actual shot at "Restoring the Republic" in the scenario where they pull off their plot?

The problem is that the political norms that had allowed the republican system to flourish had already started fraying as early as the time of the Gracchi, and had continued to decline after that, and the erosion of republican norms only became worse after Sulla. By 65, there had been nearly 200 years since that process of decline had started, and these norms couldn't be rebuilt from the top down. It'd be about as unlikely as modern France going back to being a absolute monarchy.

 

[John Fredrick Parker]

Thinking about this from another angle, I was looking at which members of the Julio-Claudian Dynasty are still alive by the spring of 65 CE, and it's actually a pretty short list -- Emperor Nero is already the last descendant of Germanicus, there's Claudius' daughter Antonia, and that's pretty much it.* She's already in her mid-30's, and widowed (and her son has already died young); so would she be likely to play a role in establishing the new regime after Nero's regicide?

The problem is that the political norms that had allowed the republican system to flourish had already started fraying as early as the time of the Gracchi, and had continued to decline after that, and the erosion of republican norms only became worse after Sulla.

I mean, the violation of "political norms" essentially comes down to the introduction and then flourishing of political violence; and it took another generation of deterioration after Sulla for the birth of normalized Roman autocracy to really take hold. By 65 CE by contrast, it had been nearly a century since the last civil war, and it was the actual absence of political violence that had become more normal for the Roman political class than its presence (especially since the killing of Caligula). I think you could make the case, strange as it may sound, that if anything, it would be easier to establish a reasonably timed period of republican rule in the aftermath of killing Nero (65 CE) than it would in the aftermath of killing Julius Caesar (44 BCE).

-----

Something else to consider -- if you look at the Third Roman Imperial Regicide** and reign of Nerva, you can clearly see how the legacy of the Second played out. Specifically, you can see how the fear of civil war explains a number of mistakes on the Senate's part -- Nerva's hasty elevation and acceptance, getting a new Praetorian Prefect (that would end up betraying the new emperor), being extremely forgiving to a number of coup plots, and a number of decisions by the new emperor and others that would eventually lead to the naming Rome's most famous general to be the new heir (and de facto new emperor).

I bring this up here because if it's possible to get rid of Nero without causing a civil war, that could have massive implications for how the Senate and Army react in the event of any future assassination-related-vacancies. (Not that there aren't other ways the Third Regicide could have gone as is, but that's a different thread.)

On the subject of Roman Imperial Regicides -- and borrowing from another thread on Caligula's regicide, since it kind of relates here too:

I'm kinda curious what the republican restoration option is like... The political order has been fundamentally changed so it should be obvious to everyone that just going back to how things used to be isn't possible, but what changes would they make?

The trick here seems to be that, officially speaking, the Senate is the one passing "acts" that the Emperor does when he governs -- like appointing provincial governors, for example -- so you could hypothetically have a scenario where they simply enact legislation without oversight, or rather the only oversight being the (hopefully apolitical) watch of the Praetorian Prefect.

The major challenge, it seems to me at least, is that well by this point the body is composed less of men who were elected by the popular assemblies, but by those imperially handpicked and their descendants, in effect being a kind of official arm of the aristocracy; the senators will be loathe to resume sharing power with the assemblies (as they had before Tiberius), and the state can only function so long before, at the very least, new blood is needed.

*There's also at least one child of indeterminate gender and age -- when looking at the children of Julia Livia, the granddaughter of Tiberius and niece of Claudius and Germanicus, the only name I see living to adulthood is Rubelius Plautus, who was already killed in 62 CE; he did have children before his death however, likely not before 55 CE, and his widow and children weren't killed until the purges of 66, so they would still be alive TTL. In any event, being minors, I don't expect he/she/they will be much of a factor here.
**the first was Caligula, the second Nero, the third Domitian, and the fourth Commodus

 

[not livius]

Looking at these three men, and I just can't help but see a move to restore power to the Senate, and a move toward restoring "Roman Popular Politics" as the driving force of government (basically, the kind of politicking that traditionally linked the senatorial class to the Roman people, kind-of-sort-of what was done in the Late Republic), as opposed to competing for the emperor's favor. And I think they might actually have a shot of making it stick -- after all, Augustus has long since solved the issue of how you keep the army loyal to the state as an institution instead of to their local commanders and/or governors (basically, by creating a payment system that takes up a majority of the imperial budget), and the Praetorian Guard, for all the issues it raised with the imperial system OTL, had indeed done wonders for negating any threat of political violence returning to the bad levels it got to when the republic was in it's later stages. I mean yeah, this kind of stability may only last for as long as Rome's rulers don't actively f*** things up, but TTL you've got them starting off on a pretty strong foot, with figures like Seneca still alive to offer their guidance.

The basic problem isn't that the Republican system is irretrievably broken, or unsuited for governing an empire, or any of that kind of thing -- it's that none of these guys know what it actually looked like. Tacitus says (about the situation in 14 CE, at Augustus' death) that no one around could really remember the Republic, and that's even more true by the time Nero dies. What they want (I think) is a system where the "best man" is chosen from the Senators by the Senators, preferably with minimal input by the people and the soldiers. They don't want a return to having to run for office or appeal to Roman citizens inside the city of Rome for power and legitimacy -- and I think that system would be difficult to justify given the vast increase in the number of Roman citizens during the Julio-Claudian period and the fact that they live all over the Mediterranean world. But "Republican" senators seem to be reluctant to do the basic things needed to secure power in Rome -- like for example Galba failing to offer a payout to the legions when he ascended to the throne or when he chose his successor.

Meanwhile the Julio-Claudian emperors were the heirs of the populares of the late Republic -- they knew they had to appeal to the citizens in Rome and to the legions. So it is still the case in the Principate that "Roman popular politics" and "senatorial power" were two different things, which co-existed under the control of the princeps. Letting the senators choose the next princeps would probably destabilize that system -- even though we do see emperors choosing their successors (Nerva, Trajan, Hadrian et al.) they are choosing from a relatively small pool of potential heirs and it's their choice, not the Senate's. We don't say that Hadrian restored the republic when he selected his successors, for example.

 

[John Fredrick Parker]

@not livius Those are very good points about longer term institutional problems; I’ll admit “Restoration the Republic” may not be the best term for what we’re seeing here. But at the same time, we are seeing something here.

First, you have members of the Senate, with the support of the Praetorian Guard, openly killing the Emperor. Then the Senators select the “best man” from themselves by themselves to replace him. Then, before the other legions can do anything, this “best man” selects the most unambiguously glorified man in the Roman Army, who none of the other legion commanders can hold a candle to, to be his heir. And it just so happens that the son-in-law and likely heir of said general has deep family ties to the same faction that the “best man” and the conspiracy that elevated him was drawn from.

Against this, who do you have? You might say “the people”, but (as goes the eternal question) which people are “the people”? There are no doubt many who are furious with this faction for killing Nero -- very well, but who do they then rally behind? As mentioned, pretty much everyone besides Nero in the Julio-Claudian family is dead at this point; and none of the other legion commanders are going to be able to make independent claims of their own, and those that might try are more sympathetic to the senatorial faction than to what remains of the imperial family anyway.

So, for the time being, it looks like Piso, Corbulo, and Vinicianus will each in turn be emperor. And given the last can easily enough live into the second century (assuming death by natural causes), that gives us about 35 years of Rome being ruled by the conspiracy’s faction. What does the Roman Empire institutional look like during this period? I imagine the Senate will feel very vindicated in asserting their “privileges” around this time; Corbulo, and probably take more notes out of Claudius’ playbook than Caligula’s or late-reign Nero’s. And without the Civil War of 69, you don’t see the Senate completely humiliate themselves, meaning you’re a lot less likely to see the psychological basis for anything like Domitian’s reign, at least for awhile.

But what about the military? Well, peace with Parthia is established for the time being; without 69, the Germans are unlikely to try anything, and it’s even possibly that Dacia leaves Moesia alone for longer; and while a Jewish Revolt may still break out in 66, Corbulo being alive (and in the government’s good graces) means it’s less likely to get as out of hand as OTL. So altogether, it looks like the frontiers of the empire are in a good position to remain quiet for the time being, which is good for keeping the ambitions of legion commanders in check.

Who does that leave? The urban masses? If the emperor, senate, and praetorian guard are all on the same page, what can they really do? Okay, maybe a handful of populares-inclined politicians break ranks to try to control the mob, maybe some imperial court attendants get involved, but… well who else is there? I’m seriously racking my brain here, and there’s only one figure I can actually see doing anything with the city plebeians, or any legionaries trying to find some way to stay loyal to a dynasty that practically doesn’t exist anymore -- and that’s Claudia Antonia.

And does she even want to do anything? She’s already been married twice, but if she was willing for a third, she could prove invaluable to the new administration; or perhaps the monarchical sentiment of the masses proves stronger than they’re misogyny, and they’re actually willing to form a faction led by her. If the latter is plausible, it could lead to an interesting political dynamic for the new order.

Thoughts?

-----CONSOLIDATE-----

Another potentially major detail here -- since this PoD is only a few months after the Roman Fire of 64, does that mean the Christian Persecutions Nero carried out OTL would be either prevented or significantly curtailed? In the short term yes, it would be a fairly minor change of note; but it's possible this change inadvertently prevents the martyrdom of St. Paul and many others,* which would have very important implications for the still very, very young religion. Now I do realize that with a PoD this early anyway, there's all kinds of ways to prevent the emergence of Christianity as a major religion in the Roman empire, much less the predominant one; but what I'm more specifically curious about here is, would the absence of Paul's martyrdom effectively prevent the survival of what we would call Pauline Christianity (or, more often, just Christianity)?

Would Judaizing Christians have more influence in the longer term TTL? Actually, that brings up potentially another very important question -- is the Second Temple in Jerusalem still destroyed TTL? I mentioned earlier how the Jewish Revolt in 66 CE may not be as likely to escalate to the point that Jerusalem is utterly devastated, as it was OTL in 70 CE. If the event were, at least, significantly delayed, wouldn't that greatly diminish the growth of a religion that promised their savior was to be the "New Temple"?

What do you guys think?

*There's some disagreement on whether the sources support it, but if do go with the traditional view that St Peter was martyred in Rome, than he most certainly would have been in the city at the time of the Great Fire; as such, he's probably already dead by the time of the PoD. St Paul, however, most certainly wasn't in Rome at the time of the Fire -- he had spent a couple of years (60-62) in the capital under house arrest, and then traveled on to continue proselytizing; given that persecutions would have started in Rome in the later months of 64, it's unlikely he was arrested again earlier than 65; and given that he'd insist then, as he did in Jerusalem, on his rights as a Roman Citizen, he would have been sent to Rome to stand trial, and likely wasn't executed before 66 CE. Given all that, it's entirely possible our PoD has messed with his fate.

 

[jacob ningen]

Another potentially major detail here -- since this PoD is only a few months after the Roman Fire of 64, does that mean the Christian Persecutions Nero carried out OTL would be either prevented or significantly curtailed? In the short term yes, it would be a fairly minor change of note; but it's possible this change inadvertently prevents the martyrdom of St. Paul and many others,* which would have very important implications for the still very, very young religion. Now I do realize that with a PoD this early anyway, there's all kinds of ways to prevent the emergence of Christianity as a major religion in the Roman empire, much less the predominant one; but what I'm more specifically curious about here is, would the absence of Paul's martyrdom effectively prevent the survival of what we would call Pauline Christianity (or, more often, just Christianity)?

Would Judaizing Christians have more influence in the longer term TTL? Actually, that brings up potentially another very important question -- is the Second Temple in Jerusalem still destroyed TTL? I mentioned earlier how the Jewish Revolt in 66 CE may not be as likely to escalate to the point that Jerusalem is utterly devastated, as it was OTL in 70 CE. If the event were, at least, significantly delayed, wouldn't that greatly diminish the growth of a religion that promised their savior was to be the "New Temple"?

What do you guys think?

*There's some disagreement on whether the sources support it, but if do go with the traditional view that St Peter was martyred in Rome, than he most certainly would have been in the city at the time of the Great Fire; as such, he's probably already dead by the time of the PoD. St Paul, however, most certainly wasn't in Rome at the time of the Fire -- he had spent a couple of years (60-62) in the capital under house arrest, and then traveled on to continue proselytizing; given that persecutions would have started in Rome in the later months of 64, it's unlikely he was arrested again earlier than 65; and given that he'd insist then, as he did in Jerusalem, on his rights as a Roman Citizen, he would have been sent to Rome to stand trial, and likely wasn't executed before 66 CE. Given all that, it's entirely possible our PoD has messed with his fate.

There's also Guerevich's thesis that Vespasian drew out the Judean revolt for the purpose of winning the year of four emperors so how does that butterfly this.

 

[John Fredrick Parker]

There's also Guerevich's thesis that Vespasian drew out the Judean revolt for the purpose of winning the year of four emperors so how does that butterfly this.

Looking him up, and his argument -- and yeah, I'd say he makes a pretty good case for that. For our purposes two aspects of the argument stand out -- first, that Nero specifically chose Vespasian to deal with the revolt (after the governor of Syria made a hash out it) precisely because he was a "nobody" who (Nero figured) didn't have the deep connections to the senatorial class needed to pose a direct threat to him; and second, that Vespasian could have taken Jerusalem fairly easily in the winter of 67-68, but dithered so that he could remain at the head of an army in the east and build his base of political support.

Obviously, TTL's Emperor Piso wouldn't be making these kinds of calculations, and whoever he picks (maybe Corbulo) wouldn't have the same incentives to either be too slow to seize an opportunity (meaning Jerusalem falls and the rebellion cleaned up circa 68 CE) or to rush the job for the purpose of achieving a quick propaganda victory (as Titus storming Jerusalem in 70 CE was OTL). Meaning, most likely, that the Second Temple is not destroyed.

 

[jacob ningen]

Looking him up, and his argument -- and yeah, I'd say he makes a pretty good case for that. For our purposes two aspects of the argument stand out -- first, that Nero specifically chose Vespasian to deal with the revolt (after the governor of Syria made a hash out it) precisely because he was a "nobody" who (Nero figured) didn't have the deep connections to the senatorial class needed to pose a direct threat to him; and second, that Vespasian could have taken Jerusalem fairly easily in the winter of 67-68, but dithered so that he could remain at the head of an army in the east and build his base of political support.

Obviously, TTL's Emperor Piso wouldn't be making these kinds of calculations, and whoever he picks (maybe Corbulo) wouldn't have the same incentives to either be too slow to seize an opportunity (meaning Jerusalem falls and the rebellion cleaned up circa 68 CE) or to rush the job for the purpose of achieving a quick propaganda victory (as Titus storming Jerusalem in 70 CE was OTL). Meaning, most likely, that the Second Temple is not destroyed.

which has butterflies as Yochanan ben Zakkai cant move the Sanhedrin to Yavne or argue against the temple in favor of gimilut hasdim. Althoug the shift was already happening the fall of the Second Temple and Masada solidified it. and Josephus doesnt defect and write for the Flavians either.

 

[John Fredrick Parker]

which has butterflies as Yochanan ben Zakkai cant move the Sanhedrin to Yavne or argue against the temple in favor of gimilut hasdim. Althoug the shift was already happening, the fall of the Second Temple and Masada solidified it.

In other words, in addition to Pauline Christianity, Rabbinic Judaism as OTL knows it doesn't exist either. Considering that additionally, OTL, this was also the period when Mithraism started to gain a foothold in the Roman World, that the religious landscape of the empire in the latter second century could potentially be notably different TTL. (Then again, it's not like any of these three "cults" were super popular before the Third Century, so it's quite possible I'm jumping the gun a bit here.)

 

[jacob ningen]

In other words, in addition to Pauline Christianity, Rabbinic Judaism as OTL knows it doesn't exist either. Considering that additionally, OTL, this was also the period when Mithraism started to gain a foothold in the Roman World, that the religious landscape of the empire in the latter second century could potentially be notably different TTL. (Then again, it's not like any of these three "cults" were super popular before the Third Century, so it's quite possible I'm jumping the gun a bit here.)

Although the MT isnt published until the 8th century and the Talmud isnt finalized until the 6th century. At this point Chicken Parm was still kosher in the Galilee.(if the dish existed) And Rabbinic judaism changes a lot in the 12th century with the Rambam and the 16th with the Shulchan Aruch and the 18th with the Mitnagdim Hasdim and Haskalah but the foundational myth is Yavne.

 

[jacob ningen]

Although the MT isnt published until the 8th century and the Talmud isnt finalized until the 6th century. At this point Chicken Parm was still kosher in the Galilee.(if the dish existed) And Rabbinic judaism changes a lot in the 12th century with the Rambam and the 16th with the Shulchan Aruch and the 18th with the Mitnagdim Hasdim and Haskalah but the foundational myth is Yavne.

And the Story of Ben Zakkai meeting Vespanian and hailing him as Caesar is highly apopcryphal in the first place. He could probably establish Yavne without Vespasian but the turn away from the temple will be more difficult if its still standing and more temple oriented cults still have it as a base of power. Thats how the Sadducees disappeared being tied to the priestly class when the Temple disappeared so did they(claims by the Karaites to be their descendents notwithstanding.)