Jake wasn't too worried about that because everyone who was close to him was out of the stock market and he himself knew pretty well when the bubble would burst, even Matthew who had billions of dollars invested gave up talking to Jake about selling the stock and just trusted him.
Furthermore, Jake knew that even after the bubble burst if people understood the stock market well they would have time to sell the stock before it went bankrupt, only those who hoped the stock could rise again would get in trouble.
Fortunately Jake knew that at that time when the internet was not so present in people's lives it was difficult to find many ordinary people who would take risks in the stock market, so few people who didn't understand the stock market would do something like mortgage their house to invest.