Migrants. North Korea collapsing is a nightmare scenario for China. Especially if it includes America nuking the peninsula.
Most of the countries in the world are against North Korea except China. Why?
WHY? Lets say China and North Korea is a business partner that China gain more benefits on it.But China is still opposing in the North Korea Nuclear program.
True, the nukes are making China uneasy but they have no option but to prop up the regime else see North Korea fall. It's pretty obvious Kim knows this.
And yes, China gets a lot of raw materials from North Korea to the point that you can say they are exploiting the country. And since North Korea have few countries to trade with, China also makes a lot selling them stuff.