Also, if it’s really about NATO, why all the nonsense about “denazification” and the existence of Ukraine being a mistake that Lenin made?
1. What should I do?
2. How do I sell it to the people at home?
3. How do I sell it to the rest of the world?
I think that accounts for why some correctly observe Putin claimed Ukraine needed to be "liberated" from all the Nazis (#2 above). It's also why Russia has said repeatedly that NATO caused the war (#3 above).
As for the actual cause (#1 above), like all wars, there are probably multiple factors, like:
1. Former KGB Putin and plenty of others longing for the "glory days" of the USSR.
2. A desire to stop NATO expansion by intimidating anyone else who might want in.
3. Removing the Zolynksy government and replacing with a pro-Russia government.
4. Solidifying access to the Black Sea and claims to Crimea.
...
ETA: also remember, if news reports are accurate, Putin thought this war would be a 5-minute cakewalk. I suspect Russia might not have invaded if they knew the cost in lives and dollars this war would bring.
How can they be? They can’t go into Putin’s head