Certainly unexpected, but it's rational as all getout. East Germany fared very well when it reunified with the west. South Korea has much to offer. And if NK is a shadow state, really run by rogue elements of CIA and similar actors from other countries, all the government would have an interest in changing that dynamic.
Is it so today? I don't know. Is it inevitable? No. But it sure makes sense. Nutcase Kim could become as a God in history, to his people, considering the change in standard of living they would enjoy.
“What would be the offer he couldn’t refuse?”