My guess is that China sees North Korea as a major problem. NK’s moves have awakened the Japanese military, which China prefers to be sleeping. If China can “quiet” North Korea, Japan and South Korea might relax.
China taking over North Korea is a win for everyone...except Russia and Iran.
I just thought it was time to include a worst case scenario in the discussion. But I certainly hope all this optimism is warranted. My eldest brother died in the early days of the Korean War, a few years before I was born, and I have spent a lot of time in S. Korea and China. So for me this is kind of personal.