I have obviously have absolutely no idea but i think the most logical reason for NK's sudden neutrality is because they aren't being sustained by China as much as they were before, so they might be running out of goods and food. The nuclear missile program also probably siphoned extreme amount of their overall capital.

I've seen numerous of articles about the relationship between China and NK drop greatly the past few years, such as North Koreans not being allowed to work on China's side of the boarder and all joint construction has haltered (such as the biggest bridge between them which is now closed)

Without China's support, NK collapsed, so if true this would Kim to give up at being the notorious rogue leader and joining the rest of the world before he will become the reason NK ends up in another severe famine such as when the Soviet collapsed.