Nuclear war doesnt need crazy people on both sides ready to ride the bomb to end human civilization. It only needs sufficiently brainwashed bureaucrats who are stuck in the process of an apparatus that believes they have their hands forced to retaliate.
edit: And just in case somebody still has any delusions of efficiency left, most of those past cases of "almost ended the world" were down to one men who had the power and accompanying backbone to overrule and /or block a strike decision. With Vasily Arkhipov it was 2 to 1 for the "retaliatory" nuclear strike against depth charges aimed at getting them to surface.