[lenticular]

This is absolutely true. Due mainly to wishful thinking as well as some bizarrely bad statistical assumptions, the risk of something like 2008 was simply not forseen. There's absolutely no reason to think that other unforeseen crises couldn't arise in the future.

[darawk]

You're right. But there's very good reasons to think that they won't come from levered quant strategies like Renaissance's. They're extremely diversified and tend to be market neutral.