I'm rather disconcerted. What happened here?

- Did Kim Jong Un sell his country? No internal opposition?
- Or did he suddenly wake up one day thinking: I'm bored of this place, these people... Maybe being USA's bitch like worst korea is fine?
- Did best korea badly screw up its nuclear weapons program such that it can no longer even pretend that it can defend itself against USA?
- Did something in USA's war threat scare the hell out of best korea?
- Or maybe something from China and/or Russia? Or lack of something?
- Seems natural that China and Russia both would prefer one fewer nuclear-armed neighbour, but are they willing to risk having yet more border clay where USA can place its military bases?

It's plainly obvious that there's no truly sovereign nation who can't defend itself, and as far as we know that still means having a respectable nuclear arsenal.

So far, the only "good" development I can envision is that in exchange of best korea losing (all? most?) of its nukes, USA lets go of worst korea, removes military bases, and Korea is re-unificated. But how likely is that? Not very likely at all.

additional information: I've not been following this in any detail, I stopped regularly reading 'news' some years ago