Bitcoin just dropped below $13k and is currently down for almost $-2k in todays trading.
I think due to the high presence in common media in 2017 a lot of people who haven't heard of btc before invested in bitcoin and they only experienced the high gains of bitcoin in a small timeframe. Now that there is a small correction they are facing fear.
Another point might be the high transaction fees and transaction duration which led to some unsecurity, because this makes bitcoin more like an asset than a currency.
Also Bitcoin Cash and other alts have been rising even more significant than bitcoion itself, this might have let some people to switch to some alts - fueled by the above mentioned points.
It also could be a slight market correction.