By the way, this was the same type of missed risk that resulted in the mortgage collapse. People who thought they were "diversified" didn't realize that a significant fraction of their assets were vulnerable to a drastic drop in the housing market because they were all ultimately tied to residential mortgages. It always seems obvious in hindsight.
That was also helped by the closely interrelated nature of the businesses - cascading collapse. It remains a significant risk in the world economy currently.
As you note, something similar happened in bitcoin, but rather than simply having a bunch of people lying about what they were doing with coins and loans, there were also those that were simply dishonest, and the diversification into other assets saw a fair share of failures (uncorrelated) and then chronic illiquidity (correlated events). What has become obvious - in hindsight - is that the average level of honesty just isn't high enough. That's without the scams, thefts, hacks and other crap that goes on.