He's also probably not an accredited investor, selling a stock short in any significant volume is not like making a retail purchase. It can be quite hard to make money off knowing a stock will crash, and that's not even accounting for needing to know _when_ precisely since most of the ways involve short dated options. I gave up after investigating ways to bet on interest rate hikes and market corrections, and just went cash heavy at the end of 2021. That doesn't make you a billionaire it makes you just not lose principle.