Why do you think the institutions are selling? What are you basing that on? I think it is the other way around. Retail investors mainly buy AND sell based on hype and twitter messages. And I actually understand that, since understanding the actual fundamentals of crypto and the underlaying economical logics is hard. Institutions and veteran crypto whales on the other hand do understand these fundamentals. I think that the institutions and big experienced crypto whales are buying up the dips created by the retail seller panicking.
And regarding why everything falls when bitcoin falls, I tried to explain that above and also here: