You're assuming both sides remain rational and calm when dead bodies get piling up and the safety protocols for mobilizing nukes get lifted.
Imagine you're the engineer involved with launching a nuke. In times of peace even if you get a phishing call to launch a nuke, you'd have second thoughts and probably take a couple more steps to confirm. In war time, you're already primed for the possibility of the nuke being used and it takes far less for a malicious actor to end the world as we know it.
Same for all levels of decision makers. It really just takes one trigger-happy maniac to make a wrong decision somewhere.
Imagine you're the engineer involved with launching a nuke. In times of peace even if you get a phishing call to launch a nuke, you'd have second thoughts and probably take a couple more steps to confirm. In war time, you're already primed for the possibility of the nuke being used and it takes far less for a malicious actor to end the world as we know it.
Same for all levels of decision makers. It really just takes one trigger-happy maniac to make a wrong decision somewhere.