One would hope that if the people in the streets are protesting then higher ups in the russian state would also be unlikely to go down with Putin. Just like Hitler's most trusted generals readily surrendering to advancing allies to ensure favorable terms for their soldiers.

That's when the generals start talking about a "limited nuclear war", and talk about survivability. The leaders don't need to be convinced that there will be small numbers of casualties, just that their country can survive or even come out stronger than their adversaries

And I'm sure there are lots of simulations that show a survivable outcome, even if it turns out to not be true in reality.

Even in the USA, there's been talk of developing small tactical nuclear weapons for use in a limited nuclear war.

https://rollcall.com/2017/02/02/pentagon-panel-urges-trump-t...

But the problem, of course, is once that nuclear snowball starts rolling, it's hard to stop it, and there's no predicting how big it'll get because leaders don't always act as they do in simulations.