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. What was the plan. And blaming the West (which won‘t be 100% justified) will not help. And he may feel that now he is applying good pressure too, with those drone strikes and knocked out refineries.
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.
There is wrong assumption here that Russia wants only those territories and not whole Ukraine. Also, the Ultimatum was sent to NATO, when Putin invaded Ukraine... and it includes aim to use force against half of Europe and justifications to use it against other half as well. Also, just like it was with Hitler, allowing him to swallow those territories did not prevent WW2... that was also in plans of Stalin to use Hitler as puppet.
So, the maximum of Russian gamble is to take over most of Europe and given that he also threatened Macron, Putin does not see Russia equivalent in power to anyone in Europe but only USA. He is that stupid - he thinks, that anyone should bow to him, because he has 4000 nukes.