> The same can be actually said about Zelensky, for whom any concessions to Russia mean political death too. If Ukraine loses territories forever, people will ask, why so many had to die for that.

That is actually not true at all. People in Ukraine know that it is not about territory but about sovereignty.

The problem of giving up territory is that you will run out of it. The goal of Ukraine is to survive as an independent state, not to hold the ground.