Why didn't Vasili II of Moscow accept union with the Roman Church?

After the Council of Basel/Ferrara/Florence ended in 1445, the East and West churches were nominally unified. Metropolitan Isidore of Kiev had been funded by Vasili II to go to the conference, even though Vasili II wasn't as convinced of the need for an alliance with the West as Isidore.

When Isidore returned, he was promptly arrested, and the union with Rome denounced. But... why? I can understand why the people and clergy in Constantinople resented the union, but what did Moscow have to gain from remaining with the doomed Byzantines? If anything, they could also have used strengthened ties with Western powers, as they were in an ongoing struggle with the Tatars. It seems like the Pope and Isidore both expected Vasili to comply; why didn't he just adopt the Latin rite? And what would have happened if he had?
 
I imagine what Vasili had in mind when reluctantly accepting Isidore's expedition was not what Isidore brought back from the Council. There's been a lot of previous attempts by monarchs and Church hierarchies to try and bridge the Orthodox-Catholic gap that have disastrously fallen apart the same way so I think that fundamentally there's a problem that can't be overcome just by having negotiations at all. The enduring examples of Orthodox churches under Rome that come to mind all involve persecuted minorities and principalities on the brink submitting to Rome's suzerainty for protection. I think just sending a guy into the lion's pit of a Council and the pontifical court and expected them to come back winning enough concessions to sooth and appease everyone back home and achieve their policies of being just Catholic enough to get aid while not actually having to submit to Rome's calendar and Rome's rites and Rome's theology, etc... is a bit optimistic. I think for Vasili to go ahead with what the Council was willing to offer required him to be essentially so desperate as to grab any lifeline, not just struggling with the Tatars but struggling with a Golden Horde just as united and deadly as his youth at the gates of the capital with a puppet at hand.
 
After the Council of Basel/Ferrara/Florence ended in 1445, the East and West churches were nominally unified. Metropolitan Isidore of Kiev had been funded by Vasili II to go to the conference, even though Vasili II wasn't as convinced of the need for an alliance with the West as Isidore.

When Isidore returned, he was promptly arrested, and the union with Rome denounced. But... why? I can understand why the people and clergy in Constantinople resented the union, but what did Moscow have to gain from remaining with the doomed Byzantines? If anything, they could also have used strengthened ties with Western powers, as they were in an ongoing struggle with the Tatars. It seems like the Pope and Isidore both expected Vasili to comply; why didn't he just adopt the Latin rite? And what would have happened if he had?

In the terms of "stick and carrot", this was a "stick": Russian Church would be subordinated not just a Patriarch of Constantinople but to his newly found boss, the Pope (aka, lowered in a rank). By defying decision of a Council he was de facto breaking with the Patriarch of Constantinople (who was under the Ottoman control) to whom the Russian Church was formally subordinated. One of his 1st moves was to appoint his own metropolitan of Russia without (AFAIK) consultation with Constantinople thus upgrading his own status (among the Orthodox states). However, if as a part of a deal Russia was offered a patriarchy of its own ("a carrot"), the reaction could be different.

Of course, usefulness of the Western ties was not fully recognized at that time but for the Muscovite state to be a part of the "Catholic world" could be quite beneficial even at the time of Vasili's son, Ivan III, especially in the areas of technology, architecture and warfare. In OTL the shift was in an opposite direction: warfare of Ivan III became increasingly Tatar-influenced (and based) and while Ivan IV introduced some innovations like an infantry with the firearms, they were rather Ottoman-influenced and not on a scale necessary to keep on a level with the Western opponents.
 
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