It's not just that these people were greedy. Some people may already have psychological issues and bearing such a huge financial loss and aggravate an already existing condition.

I've dealt with depression for years and sometimes i feel like my life is out of my control. Im times like this I feel overly invested in some things. Like sonetimes I get really worried and obssessed about the idea of earning more money. The way I think is if I can earn more money than that means that I am successful, that my life has meaning, that its not a complete waste after all.
You can imagine what such a market crash to do to a person who is so emotionally invested with financial success that it becomes a measure of self worth. The regret and guilt can very well push them over the edge.