Putin invaded because Ukraine was about to be defended by NATO, not because he fears NATO aggression.

It's remarkable that Tucker Carson, Glen Greenwald and Noam Chomsky agree with you on this issue. I however do not. Putin's fundamental motivation is not the "threat" of NATO but is instead the primitive racist idea that "Russian blood" runs in the veins of Ukrainians and therefore Ukraine must be joined to Russia. Go listen to some of Putin's speeches if you doubt this.

NATO is a defensive organization. Putin did not invade Ukraine because he was afraid of NATO aggression. He invaded because he always intended to invade Ukraine for the primitive reason I've stated above -- and the possibility that Ukraine would join NATO made it necessary to invade before NATO was pledged to defend them.