It's not about Ukraine. It's about preventing other things after Ukraine.
Maybe you think that's dumb, but saying it's about Ukraine misses the point.
There's certainly all sorts of geo-politcal shennanigans at play - as there is with any conflict. But, at the end of the day, Putin doesn't want to lose Ukraine and it's quite likely he's willing to do more to not lose it than the West is to check him.
And, if/when that happens and Ukraine becomes a puppet state of Russia, so what? It's not worth tens of millions of people dying (which is what Vindman is suggesting is going to happen) and the bulk of the west understands that. You can certainly argue for/against that approach, criticize the West when they respond to Putin agression with sanctions, etc.
All I'm saying is that Vindman suggesting WWIII is on the horizon because of this dispute is just silly - it's not going to happen.