Russian government really is just a one-man show. Whatever Putin says, goes.

That is not the case with Ukraine. Zelensky can't just capitulate, sign a deal, and the Ukrainians will all clap for him and go along. He actually needs some sort of public consensus, to get constitutional changes through and abdicate territory.

I have never seen anyone point out that the deal has to appeal to the Ukrainian citizenry, but we are all about to find out that they simply aren't interested in giving up territory they tightly hold. They hold the high ground, literally.