I read an article recently—which I'm afraid I can't find anymore—that posited that part of what's going on is that Putin, and some of the rest of Russia, has a rather surprisingly expansive view of what it means to be "Russian", combined with the belief that if one is, by that definition, Russian, it is good and right to be part of Mother Russia.

It also pointed out that by extension, this means that anyone in Ukraine who does not believe that they are Russian (and thus does not want to be part of Russia) is either effectively insane, or some kind of seditious traitor (I don't remember the exact way that logic went in the article at this point).

I don't know to what extent what it described is true (my guess is "somewhat, but not necessarily absolutely"), but it does seem to help explain some of what's going on.

I agree and this is what I've read and listened to as well. (1) Putin tell us this is the case in his spoken words and in his written words and actions.

From an economic standpoint, or the standpoint that war is bad and should be avoided this obviously looks insane to you and I. But if you have different motivations, such as you and others described, it could look perfectly rational. It's all about the parameter space you operate in that determines your actions.

(1) Ezra Klein has some fantastic podcast episodes about this - let me know if you'd like a suggestion or two