Russian fear of a liberal democracy - Mearsheimer’s words - in Ukraine comes from the fact that Russia is a personalist autocracy and its autocrat fears this. The fear is not rational in that it is a threat to Russian sovereignty or territorial integrity. It is a threat because the autocrat does not want his people to see Ukrainians thrive whilst they do not. It would make him look bad.
In no sensible way can this war be blamed on anyone other than Putin. It is Putin’s ego combined with a desire for control that caused this war. Russia is Europe’s last old style colonial empire and Putin pines for the days of Soviet domination in Eastern Europe.
Russia aggression in Moldova, Georgia, Belorussia, and elsewhere similarly can’t be blamed on anything other than Russian imperialist desires for control.