> Domino theory nonsense.

It isn't theory. It's a practical understanding of who and what Putin and the Russia state are.

The practical reality is that Russia has been expanding by increments. First Georgia: https://en.wikipedia.org/wiki/Russo-Georgian_War

Then Crimea: https://en.wikipedia.org/wiki/Russian_occupation_of_Crimea

And now they're trying for more of Ukraine.

Submission and appeasement don't lead to good outcomes.

> why did they offer Ukraine a peace deal

Russia can end the war tomorrow. All Russia needs to do is get out of Ukraine. All of it. Simple to do, easy to achieve.

That's the best peace deal Russia can offer.