Who/what was at fault for this cause for black tuesday and why

Part of the panic that caused Black Tuesday resulted from how investors played the stock market in the 1920s. They didn't have instant access to information via the internet ... The other reason for the panic was the new method for buying stocks, called buying on margin.

Black Tuesday refers to October 29, 1929, when panicked sellers traded nearly 16 million shares on the New York Stock Exchange (four times the normal volume at the time), and the Dow Jones Industrial Average fell - 12%. Black Tuesday is often cited as the beginning of the Great Depression.