Good chapter, good chapter, but as a Hungarian, who read a lot about the political history of the country during the dualist period (for a timeline I will never have the will to write) I have to point out some things that I found at least unlikely or in a few cases even outright wrong. These aren't by any margin so big to derail your amazing plans (great fan of your timeline by the way), as your research was methodological enough, but more or less nitpicks by someone, who read to much about this period and is too set in ideas about it.
First the clearest and most obvious mistake, Wekerle wasn't an aristocrat. Sándor Wekerle was famously the first commoner (more precisely he was from a family of burghers) to be elected as Prime Minister of Hungary. This still means largely nothing to your timeline, as as he became a career politician, he acclimated to the class which dominated it, aka the magnates. This meant he became a large scale landowner and generally behaved as an aristocrat, but crucially he wasn't one. He tried to become one at least in behavior as he became successful.
On Károlyi you are correct his break from the mainstream of the nationalists was inevitable, he became to much wedded to socialist sounding policies, to remain with them. Although his lack of organisational talent should harm him hard enough, but there isn't a political force in the country which has an organisation and a political platform similar-ish to Károlyi's to help him out to a degree. Wait there is one, but about them later.
On Tisza I am a little bit conflicted, Wekerle throughout his last tenure as Prime Minister complained about Tisza's undue influence over the diet and at certain point he felt that in reality Tisza commands the majority in the assembly. Tisza was a canny political operator and simply sitting behind Wekerle without making a challenge to regain the highest office of the realm sounds unlike him. He had the connection and the political capital to try something and he was power hungry enough to do so. This doesn't mean that there was no chance that Wekerle wouldn't outplay him (you don't become 3 term prime minister without being good at politics), but him sitting in silently behind Wekerle sounds like another person and not István Tisza.
It should also be noted that he wasn't as a big reactionary as you depict him. Sure he wanted to prolong the rule of the hungarian aristocracy eternally, but he unlike many of his fellow party members realised that the current system is untenable even in the short run. In fact, although almost all narrative surrounding the late dualistic hungary omits this, but under Tisza's premiership the electoral law of 1913 was accepted. This was a minor change to the electorate, raising it to ~13% of the total population and wasn't much more than a bone throne to the people arguing for electoral reform, but he was surprisingly willing to go through with that. So him going openly against the "universal" suffrage being introduced, is to me somewhat unlikely, although undeniably possible. In Fact I found it more surprising, that the same diet which did not fail in patting itself on its imaginary shoulders, for their enlightened reform, would actually vote for something as radical as happens here.
And atlast returning top the question to an organised force for reform: What happened to the social democrats? The Social Democratic Party of Hungary was the only true mass party of the country in 1918 and were one of the main pillars of Karolyi's OTL rise to power and were the reason behind his abrupt fall. The only party with a national (if city focussed) organisation and the only one which managed to organise mass strikes and a protests in the last 20 or so years (and also the nationalist parties of the minorities, before I forget them) their lack of gaining seats is highly surprising to me. The social democrats should thrive in this reorganisation of national politics, but now they are outcompeted, by a practically random intellectual from inner city Budapest and his 10 friends who decided to found a party dedicated to a fringe ideology. Alright that's a little bit harsh, as Ervin Szabó was one of the main ideological and intellectual force behind the soon to be (OTL) Communist Party, but so easily sidestepping one of the most organised political force of the country sounds still deeply unrealistic. The MSZDP should be in the national assembly by any metric, and be at least a bit higher then the Labourers which would be a party drawn in a 1000 direction by it's competing ideas about how to make a revolution.
On a similar level I found it unlikely that a small landowners party wasn't founded, as these pro-landreform, but socially conservative parties were very popular in OTL after the war.
Sorry if I'm complaining, but this is one of the few fields in history in which I feel some level of competence and I had to get this out of myself. Once again, a great story and I am very glad that you did not employ the common, but at least false tropes one could have about this period, as you had undoubtedly amazingly well researched the period, just I have my nitpicks.