Yeah, China could have a giant service with 500 million users, but it's entirely possible practically nobody outside of China would even know of its existence, save those who make it their business to know such things.
Anything "big in China" is, more often than not, just a knockoff of something first made outside of China but able to thrive within China because it doesn't have to compete with those products or services that it was made to imitate.
This what happens when you have a distorted market closed off to all meaningful outside competition.