Ok, not unpredictable.
So, Putin's demands. Firstly, you need to look at this from Putin's perspective:
1) No expansion of NATO. Well, he is running one country, and likely somewhat p!ssed off that there is a whole alliance of countries ranged against him. Why wouldn't he want that alliance to stop expanding? Putin is often criticised for sabre rattling, surely expanding an alliance clearly aimed at his country would be seen by Putin as not only sabre rattling but a real threat.
2) Troops out of Eastern Europe. You mean, he is asking that troops not be amassed near his borders? Um, the west went apoplectic when he started to mass troops on his border with Ukraine, but apparently they can amass troops near Russia. yeah, hard to see how Putin has a problem with that . . . or is it?
3) US not to use nukes defending Eastern European allies - this is what the guy in the video said but in his list he omits the nukes part. Seems reasonable really.
Ok, so the problem with Putin's perspective is that he is not looking at this in an unbiased way, then again, neither is anyone else.
Putin obviously wants greater Russia back, knows he won't get it but wants to grab any bit he can. He also wants compliant regimes near his borders. Plus, Putin knows he will not get a big reaction if he takes over Ukraine. He has already taken bits without much response so why not the rest? Why not? Because the cost may be too high, although Putin's calculations on this may not be the same as anyone else's.
It is not so much working out what Putin wants, he wants Russia to return to the borders it had after WWII, which are similar to the borders they had before WWI (actually the Russian Empire included Poland, Finland and a few other bits besides before WWI), but, hey, Europe: borders move a lot amongst the warring tribes in that region!
Yes, Putin does see the situation somewhat from the perspective of the old USSR, but so do the west. Putin does act as if the cold war never ended, but so do the West. NATO exists as a counter-balance to the
USSR, oh sorry Russia now, but NATO's existence makes no sense except as an oppositional force to Russia.
It is more a case of working out what Putin thinks he can get away with, and also that the more he gets away with the more he is likely to push. Combine this with all the other factors such as Western Europe's reliance on Russia for gas and oil, a reluctance from the USA to intervene militarily, an inability from Europe to respond militarily, and many other factors I don't know about or have forgotten, and it becomes a lot less predictable.
None of this excuses invading Ukraine, and it is not clear he has invaded apart from the parts which he no longer recognises as part of Ukraine plus some disabling of possible military opposition, but one should always seek to find out how it is explained and/or justified.
DS
Just as an aside, here is a map of the western borders of the Russian Empire before WWI:
Yeah, you can see here that Russia used to be a lot larger than it is now.