All of the crypto are down today, not just Bitcoin. Looks like a certain amount of selloff causes panic and makes all noobs dump their hands resulting in what we see today. Ripple is down big time so this is not like some banks are orchestrating this or something.
I guess one more day in the world of crypto which recently has seen a whole influx of traders who are chopping waves and this results in take profits followed by cover positions. Not to mention the SHORTS.
Most crypto tends to move together (ish). Or rather, you could say they follow bitcoin. It's the same way all stocks in the same sector tend to generally move together. If Facebook is down one day, chances are pretty good that Google, Netflix, Apple, Microsoft, and Amazon are down too.