> It was a gamble. Would Ukraine fold, or not?
It doesn't matter if Ukraine folded. Why? Because what happens next?
If Russia installs a puppet regime and leaves, how long does that puppet regime last?
If Russia stays and maintains a military occupation, it faces the prospect of a decades-long counter-insurgency from a geographically large country with 44 million potential insurgents who are really unified by their hatred of Russians. Post-WW2 insurgencies have had an incredibly high chance of success against even far more numerous and technologically superior occupying forces. It's a bad bet.
It was a gamble. Would Ukraine fold, or not? If they folded, Russia could have taken all of Ukraine, and the only price would be the sanctions. Putin could easily have thought that it would be worth the price.
The question was, what were the odds of Ukraine folding? Putin may have thought they were 90%, which would make it a worthwhile gamble. I'm not sure anyone in the West regarded the current situation as the most likely outcome, either.
So I'm not sure that it's fair to say that "a lot of this was forseeable". The sanctions were (though perhaps not to this level). NATO solidarity and Finland and Sweden joining were somewhat forseeable. I'm not sure that the rest were.