It is interesting that Bitcoin is only down 50% in the same time, that means Coinbase is not strictly correlated with BTC then. So, there must be another reason why Coinbase is down, which would be interesting to figure out.
Value of BTC is what people will pay for it now. Value of COIN is the discounted value of all future cash flows, which is heavily correlated with what people will pay for BTC in the future. COIN is doubly-levered on interest rates: its future earnings are tied to BTC, which itself tends to drop when the stop market does, but those earnings are also discounted by the prevailing interest rate. When rates go up earning lots of money from high BTC prices in the future doesn't mean a whole lot.
