The cause of the drop in the price of Bitcoin and other cryptocurrencies is due to the sluggish stock indices around the world in recent days, including the major stock indexes of Europe, Asia and the US. According to the BBC, investors are letting go of cryptocurrencies and turning to safer assets like dollars.
Even though the Dollar itself is also in cryptocurrency with the same value as fiat dollars in general and is also always safer to be stored by anyone at this time.
I don't think it's an obvious reason it's just about letting go of something just to save the bucks although it's also possible that it could be true at this point