This is theoretically possible. You just need to be super rich and you can affect its price dramatically. So, any one from the top 100 richest can do such control easily.
May be Buffet of Amazon's jiff.
It may be possible, but there is still no proof that this kind of thing is really happening.
Finding a proof for this information may be a bit hard, and if there is really someone controlling or manipulating the market, it might affect the whole market if discovered.
Although there is no clear evidence of price control but the feeling for this is very genuine because if only some people feel and tell this story, we may not be too believing and think they are just saying bullshit, the actual situation has said the opposite, so many people feel the control and manipulation in bitcoin. But even if a lot of people find out, this game is going on in the most normal way, they understand that this control is always an opportunity to achieve good profits, it's important that we swim in the right direction