Some of my friends who are professional trader on Binance and Bittrex platform also exchanged their BTC at a lowest price. I asked them why they sold it at such a loss, they replied that they thought coronavirus will badly hit the crypto market like the stock market. So, there are many people who thought that way and sold their BTC at cheapest price. I think this is the main reason for bitcoins price collapsed.
I think the panic sell was around everywhere, although I'm not much of a trader but with the way the whole world was shutting down due to COVID19 outbreak, you wouldn't blame anyone for try to stay safe. Everyone knows how bad it could be if the cryptocurrency market want to get it and i assure you the COVID19 saga was more than enough to make a huge downtrend in the market. Afterall, crisis smaller than that have caused more dip to the market in the past. It is certain that cryptomarket will always rise back but it's not easy seeing ones investment getting dip and dipper