Here’s what I think happened. Kims nuclear test site collapsed, killing many of his scientists and destroying his nuclear program. He doesn’t have the money to rebuild his facilities nor will anyone give it to him. Some radiation leaked out and crossed into China. Kim was summoned to Beijing and was told enough is enough, if you want to stay alive stop the rhetoric, stop the testing, make peace. If you do we will support you, let you remain in power, and let your country make lots of money by following our example. If you dont we will get rid of you and replace you with someone who will do what he’s been told to do.
Thats all just speculation, of course.
That is actually great speculation