Mostly false expectations, propped up news articles with falsehoods laden through them, idiot noobs with no perspective, and the dreaded snowball effect. "better sell now before it keeps dropping" Not realizing each person that does this contributes to it's downfall.
It's like when someone throws a cigarette out the window or their mcdonalds bag out the window on the street. They don't feel bad cause they justify it as "I'm only one person and it's one cigarette what's the big deal"
The problem is when enough people think this way, it becomes a real issue, now there's cigarettes everywhere.
Each individuals lack of long term thinking and personal greed causes them to want to cash out before it gets bad, which is fine and normal. What they don't get is that each one of them selling is causing an exponential effect causing the next weak mind to sell. If they just realized conceptually the more of us that don't sell, the less it goes down. Guess it requires too much patience and mental fortitude for the average idiot.