Let's say I'm a billionaire. There's a market crash. A lot of my money is tied up in the market, but luckily, a lot of it isn't. A lot of it will be safe investments or shares in profit-generating companies that issue dividends. So, while the commoner is destitute, while I may have lost 50% of my wealth, I have safe money (and passive income) I can use to pour into the market buying post-crash cheap investments. Also, because my cost of living is minuscule compared to my income, I don't have to panic-sell during the crash.

When the market bounces back four years later, I'm now 1.5x wealthier than I was before the crash (thanks to all the cheap investments), and all I had to do was move some money around.