George Herbert Walker Bush flew into China in the 1970's to help orchestrate the Sino American relations. He was there officially on behalf of the cia. It just so happens that David Rockefeller was pleased by the budding relationship.
Since they began to purchase American debt on an epic scale they have become the world's largest exporter, alongside America and Germany. They have become the world's largest lender of debt. Essentially, China has the strongest banking system in the world.
The yuan has been strengthening vs. the dollar for a long time. Maybe the Yuan has gained strength, but most of it has been due to the erosion of the dollar via inflation. It is another example of race to the bottom, but in this case the yuan seems to have decent footing in this current economic landscape.