Putin’s move in Ukraine is the classic response mandated by Russian military doctrine.
Every military man who studied Soviet doctrines during the cold war could have told you that when the European Union made moves to start moving Ukraine towards membership there would be a military response. We can also tell you that there is not a political solution that gets Ukraine into the European Union. Only military solutions.
Since the European Union doesn’t have a military worth mentioning, it behooves them to back out. This can not possibly go well for them.
Putin does have a big ego, but that is not what is driving this.
I do, however, think that grandiosity, narcissism, and essentially an element of sociopathy is at the root of pretty much every totalitarian dictatorship the world has seen. It's more than ego. It's a pathology that includes the inability to be empathic. It's not a normal person who sits up at night signing death orders, as did Stalin. I'm not saying Putin is at that level, but the fact that several of his enemies have ‘turned up dead’ raises some flags.
As a military strategist, what would your long-term plan have been to destabilize the US if you were on the other ideological side during the time the USSR was collapsing?