My view is, at the moment bitcoin is the gateway to to crypto world. There aren't many places you can buy alts with fiat money, only bitcoin. So when people want to cash out on their alts they will trade them for bitcoin and then cash out to fiat. I might be wrong, but when you look at the movement on the prices the altcoins walk hand in hand with bitcoin. But this might not be the case in the future.

I still wish bitcoin will keep soaring and not go anywhere soon.