By daytraders, the street, and institutions.
One day, these traders run the stock up, and the next day, they short the stock.
There is no reason---no news to short the stock. What you are seeing is a game....
Those lacking knowledge, are thinking OMG, I don't want to miss out, so they get caught---become a bagholder.
And, these traders know exactly how to do it---It is intentional.
The pot stocks are the most volatile----due to stock runups and then shorting.