Which is kind of the point. Everyone involved in the process from the leader at the top making the call, to the individuals manning the silos, has to make a conscious decision to end the world.
No, the point of mutually assured destruction is to ensure that retaliation is credible and even perhaps automated.
You seem to have it backwards. The only reason we are alive is because the designed system that was built failed following a computer error. The point was to respond.