I don't think China alone is controlling bitcoin. There are some other players all over the world that can control bitcoin's price as well. Whales hold a lot of bitcoins so if they all decided to dump the coin, they can lower the price of the coin a lot. If they want to pump the coin's price, they can make it pump as well and bitcoin is a universal currency and have anonymous characteristic therefore it is not so easy to control it by a country, although it is a fact the chines users of bitcoin are more that any other country but still they cannot control bitcoin because of it universal and anonymous characteristic