And China sure doesn’t want to rebuild the place. It’s such a basket case it would probably be one of the most expensive reconstructions ever. The infrastructure has been in a shambles for years.
I see the endgame as this.
China, the US, and South Korea secretly draw up a plan to invade North Korea. Essentially North Korea will be split into a Chinese Zone and a US/South Korea zone, the main purpose is to avoid refugees fleeing into South Korea and China. Eventually the US pulls out once the situation is stabilized, and the North is jointly administered by China and South Korea, until the situation is stabilized enough for Korea to reunite. By then they will be in the Chinese sphere of influence, as part of the deal.