I still don't fully understand why all the alts drop so much, 30% 50% when bitcoin goes up $100. Who is doing the dumping, big investors or the herd of day traders? Sure these coins are traded against btc, so your coin is worth about the same in dollars, but it's not traded against dollars, it's just worth less bitcoin when it goes down. Does anyone really know why alts always do this? Are people expecting bitcoin to jump to $10 000 over night? I have heard that when bitcoin goes up there is more money injected into the system so alts go up as well, but they never do. When alts recover in a few days they bearly make back what they lost.
Several different motivations behind this trend but some of the main ones are that it's not just BTC that people are switching over to but ETH. When they see the big coins on a run they want to convert over to enjoy the profits. People also expect their alts to consolodate after a run up and they want their money to continue working for them so they get into another alt or back to BTC/ETH. Also, yes...plenty of new traders/investors that try to abandon ship when they see things in the red.