There is little danger to the economy from banks serving as custodians and transfer agents for cryptocurrencies. Nor do I think that investment firms that make investments in cryptocurrencies for their clients is a risk to the economy
No, I don't think so. That has been demonstrated again in the recent price collapse in crypto. While Bitcoin and other coins lost 20-30% in a very short period of time, it didn't have any impact on the stock markets at all. So there is no identifiable correlation and that makes crypto not a threat to the economy. And one trillion total market capitalization sounds like a lot, but in this day and age and in global comparison, these are still rather small sums.