Like everyone else is saying, Many governments trying to find ways to regulate or ban BTC (Chine, Korea, and US partly). Not to mention the entire Bitconnect platform collapsing on it's investors. Many people are just wanting to cash out any and all possible gains they have made at this point by panic selling. The price of BTC is far too high for it's purpose at this point and those invested over 1m at the beginning of last year can literally dip the market into red, all it takes is a few more of those kinds of investors to follow and some FUD and we get a flash crash.