It's a good question who controls the bitcoin. I think a group of dev controls it. Because for bitcoin, there are some private keys (for checkpoint and alert) that if one has it, he will be able to propagate his own blocks into the network. I think a few people hold the private keys there.
bitcoin is not under the control of a single person or group, because they cannot hae access to all the bitcoins address and wallets that belong to a particular person. to me those people who are holding bitcoins are the real owner of bitcoin and they can control such amount of bitcoins.
although most of the people think that Chinese are controlling bitcoin but to me i do not think so, i think bitcoin is a universal decentralize currency of the world and is not going going to be under control of a single country, actually the users of bitcoin are spread in all over the world and therefore it is as comparably hard to turn it as decentralize currency.