You are of course correct that Ukraine officially gave up the non-alignment in late December 2014. What I have to check is whether in late 2013 or early 2014 there were any indications that Ukraine might reverse course.

The Maidan revolution was certainly one such sign; it was about joining the EU, not NATO, but the two are somewhat correlated.

Sure but I do not think that I would have seen Maidan in general as something that warranted more or less immediate action from Russia. Either I really got this wrong or I must have come across something more relevant.

I think it is fair to assume that in general the USA prefers Ukraine in NATO over a neutral Ukraine and that over one oriented towards Russia. In NATO there are at least some countries that preferred Ukraine remaining neutral. Even if everyone always says that it is a sovereign decision that does not preclude them from at least having preferences. But there is at least some evidence for outside influence to push Ukraine into a certain direction which goes beyond just having a preference.

I did a bit of reading yesterday but I have not yet found anything I consider strong enough to support my Russia reacted point of view. At least at this specific point in time, in general I still have no reason to doubt that a NATO membership was the desired outcome. So currently I really tend towards I got this wrong and I am mostly held back only because I looked into all this in quite some detail after the invasion started and that seems like a mistake I should not have made.