Right now, short interest in stocks is very low. Why? People who try to go short have been getting burned by the BTFD mentality, especially in (SPY). But at the same time, risk vs reward for long positions in stocks, at least overall, is not very good.
I think a lot of the inflows we have seen into $BTC and other cryptoassets, has been coming from those traders who would, under normal circumstances, be shorting the stock market.
But what happens when enough of the BTFD euphoria runs out? Well, Bitcoin has had a good run, and it may very well continue to have more, but it is high risk, and how much reward we get from here on out is questionable. I think a lot of money will return to short positions in the stock market.
This situation would cause a waterfall effect, as short interest grows and grows and money shifts from $BTC to shorting stocks. When this result will happen, I don't know. I don't know if it will even happen. But the risk of a massive stock sell-off, boosted by outflows from $BTC, is real.
Disclosure: I am/we are long VIXY.
Additional disclosure: Generally short stocks and long volatility.