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.
Very soon (at the end of 2018g), many countries of the world will adopt a legislative framework for the recognition of bitcoin in their countries. Many banks will start attracting investors. The big whales will start to come in and insurance their money through banks in bitcoin. It's a complex scheme, but it will. Large investors want to insurance their risks in the cryptocurrency. And the Banks will help them.