I have no idea at all about the thinking of the people involved in the actual decision making and I'm pretty sure anything I read about Joe Biden or Vlad Putin

I have no idea at all about the thinking of the people involved in the actual decision making and I'm pretty sure anything I read about Joe Biden or Vlad Putin in this regard is propaganda that should not be trusted. So let's take an angle that leaves them out. There's a nuclear "exchange", maybe it's one way, that doesn't involve my country. Why would I want to get my country involved in that exchange? That seems to go from utterly terrible tragedy that is almost as bad as can be imagined to so, so much worse for so many more people. In fact it takes it to every bit as bad as possible. Given that reality, how much deterrent are they unless it's mutually assured destruction? "Is this something for which the only option is to end current human civilization?" Nasty things to think about.