It's not much of a strategy-more like something that humans have done in every game played since there were games. Also, it seems that you, like many others here, are completely mystified by the possibility that many "new recruits" have indeed played Risk before. Quick way to lose points.

A couple things about the military powers of China, Russia, and the U.S. Like many have said, China has virtually insurmountable defensive capabilities but no offensive abilities (besides overrunning SE Asia, but that would be it). So China could easily defend itself on the ground, but couldn't ...

That's nothing special. Considering that CC isn't the only place anyone has ever played a certain strategy game, it isn't even close to unreasonable that someone with extensive experience and a bit of luck can win a bunch of games right off the bat, and keep winning, especially with classic maps.