It's not a crash its a correction...
That means value has to move around....
Bitcoin is overvalues vs. the rest of the market...
So when the value goes down vs. some coins, because its a defacto fiat.

With approximately 1/3rd the market capitalization.
It looks like a crash ...It isn't...

I wrote an article on this days ago, tell me what you think...
https://steemit.com/bitcoin/@richatvns/reality-for-cryptocurrency-market-volatility-why-it-will-continue-this-year-simple-and-clear-reasons