Why did people invest so much into stocks in the 1920's?

People invested heavily in stocks in the 1920s due to a combination of economic prosperity, optimism, and the availability of credit. The post-World War I boom led to increased consumer spending and industrial growth, which fueled confidence in the Stock Market. Additionally, the rise of margin trading allowed investors to buy stocks with borrowed money, further enticing them to invest. This speculative environment ultimately contributed to the stock market crash of 1929.