The American economy was strengthened by the disaster that World War I had caused in Europe. The United States of America became the main creditor country on the planet. US investments and merchandise began to dominate the spaces in European countries.
In mid-1928, US investors restricted the purchase of bonds in Europe, especially German securities, and channeled investment funds to the New York Stock Exchange.
The prices of the shares rose quickly. The speculative wave attracted even people from the lower middle class who bought shares with family savings and bank loans.
And on October 24, 1929 there was a massive sale of shares on the New York stock exchange that ended with a dizzying drop in prices.