It is Russian. It is on Russian territory (according to Russia).

So it does not matter whether the rest of the world considers it to be Ukraine, the Russians consider it to be Russian.

Putin had a huge public ceremony last September to announce that these areas were now part of Russia, and the people living there are Russians, and will be so "forever".

That is now what the Russian people believe.

It would not be a good look for Putin if the Russians declared a place to now be part of Mother Russia "forever" and then 10 months later set off a nuclear catastrophe that would poison "Russian lands" and "Russian people".

And there is no way that Putin will ever have to give it back to Ukraine.