And just what history books have you been reading?
The boom times of the 1920s were based on money that didn’t exist except in bookkeeping records. Rich people bought corporate stock on margin meaning they didn’t have to have the money to pay for the stock they bought while everybody else bought what they needed or wanted on credit.
As long as stock prices went up nobody had to actually pay for the stock they bought because the stock ended up worth more than the purchase price. But the price for the stock only went up as long as there were people that wanted to buy it. But when the crash came stock prices fell below what they had supposedly been purchased for. The sellers then wanted the purchase price paid in full even though the market value was not worth the original purchase price. Millions upon millions of dollars that never really existed in the first place left the economy.
The same thing happened with consumer credit. Factories were built to supply the demand for consumer goods that were bought on credit. And when the stock market crashed the money for this consumer credit dried up. With no more money available to be borrowed consumers naturally stopped consuming because they didn’t have cash in hand and couldn’t borrow any more.
For both corporate stock and consumer goods the supply was unnaturally high because credit allowed buyers to buy more than really needed or wanted.