I think one of the most important factors that possibly affect the value of bitcoin is its popularity and demand for it, just as the owners of a large number of bitcoins can influence the price.
So we can say that a threat to popularity is a threat to the demand of the coins and it will result in price drop. Quite logical. Not just that but the growing number of hackers in the market makes it uncomfortable and risky to invest in crypto.
This leads to price drop. One has to have the important skills to keep the wallet secure. Volatility is another reason due to which in the down market, people sell their coins and it further drops the value. Government ban on the technology is another reason among many.