JK Rowling (of Harry Potter fame) also exited the billionaires' club, but due to charity. Slight difference... I guess we could say Einhorn donated to the markets...
Actually I think greed is one of the reasons many traders failed. The other by the way is fear/panic.
Greed is simply a form of fear, a dialectical unity. Both are normal instincts, their intensity differs among individuals and within the same individual, depending on various factors. Greed is a fear to be left behind.