You are judging him from the "good for the state" position, but in reality dictators work from the "good for them and their family" position, and he is quite rational in that.

NK nuclear program worked as a blackmail tool - they were getting aid in exchange for concessions like freezing plutonium-related facilities, though not terminating them.

Besides that, Gaddafi was a "responsible" leader and terminated his nuclear program. Dictators are paranoid, don't you think Kim Jong-un learned his lesson?