Answer:
During the stock crash, most people were trying to trade the stocks, mostly to sell overpriced stock that had lost a great amount of value in only a few days.
Unfortunately for most of them, these stocks still lost a great amount of value, which meant that they lost a lot of money. Billions of dollars of market value were wiped out in a single day, leading to thousands of people to financial ruin, and starting a period of economic recession known as the Great Depression.