But it's nearing mania .. if their own collapse is causing them to interpret negligible events to the point of invasion, anything is on the table ?

I know _nothing_ about geopolitics but don’t your questions presume that the “Ukraine joins NATO” is a real reason for the invasion?

If it’s an old fashioned land/riches grab then their current behavior makes perfect sense.

Agreed, anything is on the table. And that is what worries me, if you start assuming rational actors none of this makes sense but if you start assuming non-rational paranoid mafiosi with nukes it starts to all look a lot more plausible. Putin needs to succeed in subduing Ukraine or he will be thrown under a very large bus and then you have the next worry lined up: who will replace him, which could very well be worse.

People seem to make the mistake of thinking about this in some kind of game theoretic way where Russia would have something to gain or lose but that's the wrong perspective, Putin couldn't care less about Russia or the Russians, what he cares about is to cling to power until he's dying, if he can't do that then his lot could well be worse.