I think one of the factors that can affect the bitcoin price is bad news or FUD's that can holders sell their bitcoin because they think that the price of bitcoin will drop and the other factor is there are some group of a pump and dump that can manipulate the value of bitcoin and the other thing is there are many scammers out there that use bitcoin as their presentation that is why people didn't trust bitcoin because of this reason.
There are many reasons or factors that affect the value of bitcoin. Here are some reasons of its price to vary. One of it is the number of people or the population of Bitcoin users. I think that it affects its value. The more the people were engaged at BTC, the less its value will be. Another thing is there are people that pump or manipulate its value. These are some of the reasons of the varying price of BTC.