From what I heard from Ukrainian friends, the primary matter here is the corruption. President has criminal past, he did time for rape (!) and some petty theft, when he was younger. He was retroactively cleared of charges. Also, strangely enough, all people involved in those cases can longer be found. However he still has strong ties with the criminal world and under his rule and with his assistance existing businesses were routinely and forcibly taken over by an equivalent of mafia. All latest developments with criminalization of government critique, suppressing the right to protest, etc aren't really surprising to anyone there - it's a logical development of things going downhill in past few years.

Sure there's Russia' involvement and geopolitics, but it does appear to be a secondary matter.