It's not all China's doing. China was letting NK skirt the sanctions by letting NK produce product in China to get around the sanctions, they were also caught shipping coal into NK...the Trump administration called them out on it. That's what it takes to force people to come to the table. The very carefully crafted media presentation of bringing his sister onto the world stage during the Olympics was also a crucial factor promoting the benefits of being accepted instead of banished on the world stage. China had the ability to do this all along but never did, this was crafted, in my opinion, from the first meeting at MarLaGo between Trump and China, the plan was laid out, agreed upon and Trump didn't just let things slide back into their normal behavioral patterns he kept China focused.