I guess this happen because of crowd's panic. People bought BTC for $ 19k see it's decrease to $ 10 k , sell it, and that caused BTC go down even more.
normally if there's huge decline then people are suspecting the whales are responsible for the the game.
although partly true but I don't think someone or some groups are manipulating it because this year there are full of FUDs and FOMOs that been affecting the entire crypto market to fall over 70% from it's highest market cap this early January before the market declined continuously.
the only option I Have is to hold my Crypto Assets and not to sell them off out of panic.