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.
Yeah i think we are the only who control bitcoin since if we are not investing and buying more bitcoin the price will not increase and bitcoin is decentralized even china has a largest bitcoin farm they are just holding a large number of bitcoin but we are not centralized..