I'm sorry but anybody who thinks this was about NATO getting close to his boder needs to have their heads checked. We could have disolved NATO 10 years ago, he'd still have invaded.
Go watch Star Wars, it will tell you everything you need to know. This is about power. My neighbour is from Russia and she said that Putin's Russia will not be happy till the world recognizes their greatness and the empire is restored. They are embarrassed that they don't have their empire anymore, they have never gotten over it.
In summary:
* Putin is a mega narcissist, he wants to restore Russia into a super power and empire. Anybody who believes a word that comes out of his mouth that is to the contrary, get your head checked. Just look how competitive he is. He cannot stand that the USA is where it is compared to the shell of the USSR he presides over.
*He was going to invade, NATO or not. He is not dumb, he is a patient and calculating man. We could have guaranteed no NATO. Hed still be trying to reclaim Ukraine. Fact.
*If he wasn't limited by his own lifespan, he'd 100 percent try and march all the way through Europe, maybe not at once, but little bites at a time. What his successor will do is anybody's guess.
* He guessed right on the west not wanting to engage directly with him him. He guessed wrong on our willingness to reunite and isolate him and bleed his economy for all the Ukrainian's hes killed, even if it hurts ourselves in the process. He was banking on the world not caring about dead Ukranians. He's actually affirmed that NATO needs to exist, and the Europe needs to rearm itself, which Trump did have right IIRC.
*He, like most emperors before him, gives zero shit about his own people. Russia is like home ownership. He wants the grandest home, the bigger the better. But it's HIS Russian empire. Calling him a president is about as accurate as saying Russia has freedom of the press. He is a Czar in presidential clothing, what he wants goes.
If Ukraine is restored to mother Russia, the same song and dance will come out in 10 years about say Poland. It's too close to his border, he'll slowly use information warfare to attempt to internally fracture Poland so that he can get it.