Elon musk has been a big supporter of cryptocurrencies even helped in increasing the value of btc earlier this year though he said few things on Twitter that actually caused the fall of price, made the market to dump about 30%.
He's not the only issue that made the market to dump China Banking Association warned member banks of risks associated with digital currencies. Other digital currencies suffered sharp declines as well and the dump wasn't on btc alone even ethereum dumped to $2k.