This is correct. Putin has seen Ukraine turn more and more westward. Flirting and thinking about joining the EU and NATO. Which would mean "NATO" (US) troops right over the board and mere hours away form Moscow. Simply unacceptable to Putin.
Ukraine also has a corruption problem.
I think NATO will keep Ukraine on the cusp for 20 years like they did with Romania, before they allow them to join.
And madman though Putin may seem to be, he knows NATO isn't an offensive organization.
And I'm going to judge Putin by his own words. He says he's threatened by NATO on his borders? Then he shouldn't have 70% of his military on the border of Ukraine. It leaves him wide open to an invasion from NATO members Estonia and Latvia.
I think he may legit see it that way: https://www.youtube.com/watch?v=MOkl2XgZlw0
Sure, like the defensive bombing of Libya by NATO.