>While there was a push from the US government for Ukraine to join NATO back in 2008, it was rebuffed by the major European members
I don't think that counters anything I said. US is pushing for Ukrainian/Georgian membership, as you say. When that was put on the table, both countries began working towards achieving that membership. Considering US funds 70% of NATO, it's not implausible to think that the US will have their way in the long run. (Rational speculation)
>Even in March 2014, a month after Russia began taking over Crimera, Ukraine had no intention of joining NATO. > In fact, their constitution prohibited it until 2019
Which president? The one that was elected after the coup? Or the previous one who was pro-Russia? Mearsheimer discusses that history in his lecture I linked in my main comment. I haven't read into this but it seems likely that total national policy shifts take time. You're talking about one month to 5 years after the revolution. You have to remember half the country is either Russian descent or speaks Russian. It seems like a necessary guarantee to maintain peace with Russia.
> but a stable, democratic, and economically prosperous Ukraine that might even be an EU member.
Russia does not want that either. Over the last decade or two, Russia has been building new gas pipelines that circumvent Ukraine for this very reason. Ukraine collects a tax on all the gas that passes through their boarders. Also notable is the recent oil/natural gas reserves discovered in their territory.