1) really? You don't understand how Putin running massive amounts of energy to Eastern Europe undermines NATO?
2) Well, soon after the plans were withdrew, Putin invaded Europe. So, defense makes a difference.
3) never said they were, but they are in Europe, and were working towards potentially joining....and a war in Europe, has a drastic impact on NATO.
4) I think he invaded because he wants to recreate the Soviet/Russian Empire, and wants Moscow to continue to have massive influance on Eastern Europe...he found Obama and Xiden to be weak, and realize it was his best options to invade...in particular since they were his puppets