Putin is "committed" so to speak, so this is just following his current strategy through to its conclusion: force the West to give up on Ukraine or accept massive escalation.

The fundamental question is - is NATO committed enough to the Ukraine cause to demolish Europe? Probably not.

Everyone talking about Russia being "already defeated" knows little of the Russian capacity for misery. Napoleon learned the hard way. The Russians also accepted losses in WW1 and the following civil war that would have destroyed most other societies (and indirectly destroyed Russia too), and of course, they continued fighting in WW2 when most democratic societies would have surrendered. Do not underestimate Russia.

Compare losses in the Brusilov Offensive alone to all-time combat losses for most other nations (including the US)...Russians will keep fighting long after it seems sensible.

Eventually Biden and Blinken will back away from Ukraine...the US public will find another Current Thing to obsess over, and US troop commitments are completely out of the question.

Basically, Russia gets Ukraine eventually, its just a matter of how bad the carnage is