What if there had simply never been any Jewish diaspora?
The specific challenge is, with a POD no earlier than 73 CE (fall of Masada), for Israel to remain the home of the majority of the Jewish people.
The easiest solution is probably no Bar Kokhba Revolt. Perhaps the Romans take a more nuanced approach to governing Judea after the Judean Revolt of 67. I could see Vespasian, who crushed the revolt and then became Emperor, thinking "I never want to go through that mess again". So after breaking the Jews down, he builds them up. His policy is not a Judea that is broken and unable to revolt (or pay much in taxes), but a Judea that is accepting of Roman power, even grateful for it.
One area of common ground could be combating the spread of Christianity. Vespasian had permitted the establishment of a new Sanhedrin at Yavneh - he could have given it some political teeth, Imperial endorsement, in return for Yavneh supporting his policies. In the long run, Rome would want to raise Jewish auxiliaries and eventually permit the return of the Sanhedrin to Jerusalem and the rebuilding of the Temple. Perhaps Hadrian (or whoever replaces him) chooses to simply invest in Caesaria and make that the capital rather than turning Jerusalem into a Roman city. The Jews might be permitted to govern from Jerusalem, but banned from constructing high walls. The key is to grant the Jews power in Judea, but make that power dependent on Roman support. The hardest part is for the Romans to accept that in order to keep the Jews loyal, they must be allowed to practice their religion.
Assuming there wasn't another revolt (or at least that the Sanhedrin opposed any revolts), then the Jews become secure in Israel once more. The question is, what now? What is the impact on Christianity and Islam? Would there be a low-grade diaspora with small Jewish communities throughout the Empire? How many Jewish states, how many Temples, might there be?
The specific challenge is, with a POD no earlier than 73 CE (fall of Masada), for Israel to remain the home of the majority of the Jewish people.
The easiest solution is probably no Bar Kokhba Revolt. Perhaps the Romans take a more nuanced approach to governing Judea after the Judean Revolt of 67. I could see Vespasian, who crushed the revolt and then became Emperor, thinking "I never want to go through that mess again". So after breaking the Jews down, he builds them up. His policy is not a Judea that is broken and unable to revolt (or pay much in taxes), but a Judea that is accepting of Roman power, even grateful for it.
One area of common ground could be combating the spread of Christianity. Vespasian had permitted the establishment of a new Sanhedrin at Yavneh - he could have given it some political teeth, Imperial endorsement, in return for Yavneh supporting his policies. In the long run, Rome would want to raise Jewish auxiliaries and eventually permit the return of the Sanhedrin to Jerusalem and the rebuilding of the Temple. Perhaps Hadrian (or whoever replaces him) chooses to simply invest in Caesaria and make that the capital rather than turning Jerusalem into a Roman city. The Jews might be permitted to govern from Jerusalem, but banned from constructing high walls. The key is to grant the Jews power in Judea, but make that power dependent on Roman support. The hardest part is for the Romans to accept that in order to keep the Jews loyal, they must be allowed to practice their religion.
Assuming there wasn't another revolt (or at least that the Sanhedrin opposed any revolts), then the Jews become secure in Israel once more. The question is, what now? What is the impact on Christianity and Islam? Would there be a low-grade diaspora with small Jewish communities throughout the Empire? How many Jewish states, how many Temples, might there be?