This is how and world has always been. Might makes right. That’s why the Us ha wages all those wars. Strategically Putin did what he had to do to maintain Russian security. Just like how he Americans embargoed Cuba all those years and almost had a war with the USSR during the Cuban middle crisis. Was that greed and ego? Perhaps but it was mostly strategic security.
i see why people would view it this way and i don't disagree with you but i just want to point out a couple of things .
1. Russia is a state that would never going to be attacked by the west because they have nuclear weapon. therefore even if NATO was their next door neighbor like let say the three Baltics states Russia is not in danger of being invaded. only way i see Russia going down is from within.
2. I would say yes that greed and ego did cause the Cuban crisis. but that's prob a topic to be discuss in another thread.
3. also the greed and ego thing goes both ways. their was definite plenty of those in the west, greed due to the military complex( the amount of ammo and weapon we would give to Ukraine is big money.) ego cause the west didn't have the courage to momentarily look weak by flat out saying Ukraine wont be allow to join NATO. this will at least cut off one excuse that Putin can used to invade. even thought i doubt it will make a difference cause i think the plan to take Ukraine was going to happen it just that Putin saw an opening after covid impact on the economy( betting sanction won't be has hard or long cause economy will suffer to much, result on this is yet to see but Putin might be right on this, inflation)