What factors caused the stock market crash?

People buying on margins caused the stock market crash.

Explanation:

The prices of the stock had risen first before 1929 which made a lot of people buy the stocks but then all of a sudden the prices of the stocks started falling. This made some people buy more stocks that it would rise further while others sold off their shares. But there was more fall in the value of the stock. There fore there was a lot of sale of shares on that day making stock market crash more.