I kind of wonder how much depends on the ticker symbol. Bitcoin = BTC right? Not BCC or BCH or BTC1 or whatever else.
Bitcoin is BTC. Who decides this? Top exchanges. That is a lot of power resting there.
Exchanges have a lot of power. Most heavy miners send their coins straight to the exchanges so they ultimately end up being puppets to the exchanges. If an exchange decides to go one way then they alter their miners to ensure that they are making the most profit at the end of the day.
In a way it's kind of ironic/hypercritical. Bitcoin is meant to be decentralised but the lack of trust and power given to small exchanges means that the bigger exchanges are the ones calling the shots at the end of the day
i agree with parts of what you said not all of it. for instance you are correct that exchanges have a lot of power but this power has been diminishing as the total trade volume spreads among multiple exchanges instead of all of it being in one place.
and as other comment said above me, miners don't send their coins to exchanges. they do it off the market if they are big mining farms and smaller miners get paid small amounts that doesn't matter where they sell.
and finally bitcoin is decentralized not bitcoin price. it is a free market, the price will eventually be set based on supply and demand even if the short term is looking weird.