I agree with much of what you say, but the calculus of a nuclear war is very different than a calculus of a conventional war, or even a political system in which you murder tens of millions of your own people, and enslave even more.
I disagree that was their mindset. In a conventional war, or a political action where you are going to kill others, you likely hold out the mindset you will not be a casualty, it will be everyone else BUT you.
But there is no escaping that except for a select few (and even then) in a nuclear exchange, nearly everyone is going to be a casualty.
That said, I do agree that if Stalin had been healthier and held power another ten years, there might well have been another world war, or at least a large one.