There is a old saying in Korea, "Every grave has their own reason why he or she died."
Everybody dies finally. Actually the reason why he die is not important. Because even though he could avoid the reason, he would have another reason he die such as car accidence, or health problem.
When I ask my economics friends "why did the Great depression happen?", they usually answer it is because of the money currency. At the time, people used fixed currency, and it caused depression. Or some of them said the Federal government used wrong policy.
However, I don't believe they are real reason for depression. Because if it was real reason, now we could know how to avoid the problem, depression. But it hasn't stopped.
One of good examples is Korea economics. In 1997 Korea suffered depression, called IMF period. The symptom was very similar with the Great depression: many banks had been closed, many big companies bankrupted one by one, and unemployment ratio dramatically increased.
I think if I research more I could find more examples that the economics depression never stop. Because encyclopedia says economic panic periodically happens, generally saying the period is about from 7 to 10 years.
The real question is not "Why he died," but "Could people not die?." I think none of economists have explained it, except Marx.