every single one of us in aggregate decide the price of bitcoin through our actions, so the changing price that you see in bitcoin is the change in perception of its price and what people are willing to pay for it, however do not confuse price with value, if the price crashes from one day to the other as we have seen many times in the past this does not necessarily mean there is something wrong with bitcoin and its value remains the same, even if its price changed significantly in such a short amount of time.