The realpolitik of this is that the west is walking a tightrope between supporting Ukraine and not wanting to humiliate Putin, which could trigger a wider conflict (read: nuclear war). I believe that under the circumstances, what is targeted by the west is some sort of compromise which will save Putin's fascist face and at the same time save the lion's share of Ukraine (read: stalemate). In the end, Ukraine will have to cede some territory in order to placate the Russian bear and send him home. They'll end up with the Donbas (and Crimea) but that's about all. They won't get Odessa, and they won't landlock Ukraine.
I'm not saying it's right or just (it isn't), and I'm not saying Russia would actually use nukes if backed against the wall in Ukraine. I'm just saying this is what I think is going on, and this is the needle the west sees itself as needing to thread. And I can understand that thinking. Overlaying all of this is Putin's health and the uncertainty of when he'll go and what happens after he does. He'll probably be replaced by a like-minded despot, but one who may be a more circumspect and practical.