That is exactly the problem. Suppose the Plutonia government sincerely believes, that as soon as other countries will be protected, they will help people of Plutonia to overthrow the government? And they kind of have reasons for such belief. Then (in their model of the world) the world protected from them is a deadly threat, basically capital punishment. The nuclear war, however, is horrible, but there are bomb shelters where they can survive and have enough food inside just for themselves to live till natural death.
That is exactly the problem. Suppose the Plutonia government sincerely believes, that as soon as other countries will be protected, they will help people of Plutonia to overthrow the government? And they kind of have reasons for such belief. Then (in their model of the world) the world protected from them is a deadly threat, basically capital punishment. The nuclear war, however, is horrible, but there are bomb shelters where they can survive and have enough food inside just for themselves to live till natural death.