They thought it was a good place to make money and it never went down for 8 years in a row so everyone thought there's no risk. They knew they weren't going to make a ton of money putting it into the bank. So in the stock market, you can take $5,000 and make it worth $10,000 in that time. So people thought they could get rich. However, there were too many small investors investing as well. They also borrowed money on leverage to invest in.