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.
On the flip side of FUD (which is overused) is the perpetual hypers and the bandwagon mentality simple investors have. The reason Bitcoin reached $19,000 last year is because people without any critics thinking skills piled into Bitcoin thinking he gravy train couldn't be stopped. It was reckless and the price was undeserved. The price reached that level primarily due to hype and unrealistic expectations, and people who bought it that high pretty much got exactly what they deserved.