I think it's mostly economics related

Undoubtedly, that's why sanctions work, but they let their oligarchs keep control despite the economic disaster of the post-1991 "experiment", and that's partly because of propaganda ; they also considered that there was no viable economic model to their East despite China's rise, and that's also partly because of capitalist-induced propaganda.
Their institutions right down to even their statistical institutes were already controlled by the west before 2014, and almost each of their minister of Culture came from western Ukraine(, excepting Ivan Dziouba and Iouri Bohoutsky), among dozens of other things, without counting western lies(, one out of so many, e.g.).
So while socio-economics clearly are the main driver behind leader&population decisions(, it's not straightforward, the quick catch-up after the 90s curve is less surprising than a country (re)starting from zero like the PRC or african countries, i also have many doubts on the pertinence of the GDP), i'll still continue to accuse propaganda when it affirms that there is no alternative 🤷.
That said, fighting the Empire means that your population will suffer for your idea(l)s, no doubt that Ukraine would be sanctioned for joining the Russian Federation, and develop perhaps even worse economic difficulties than until now. Russia knows that, and won't promise them an economic miracle if ukrainians (re)join them.

Well, who knows, but we may apparently not wait for the midterms before "liberating" iranian women from anti-zionism(, if not this year then afterwards) :

Fuck the US, n°1 terrorist state on Earth, as per usual.