If chaos breaks out in NK, China will have a massive refugee problem.
It's an unknown how bad NK has the China Virus. They probably have a bad, and it wont be as effected by seasonality like other places since NK is dry and cold. So if China gets a flood of NKs, good chance it will cause a resurgence on top of the refugee problem.
Chaos would make it extremely easy for the US to amp up it's presence in the region, which will fuck with China, but Trump might not do that unless SK offers us a lot of money for it. Either way, this is advantageous for America and a nightmare for China.