If it was that risky, they wouldn’t have these assets. People have investments because they understand cash alone won’t grow. Someone like Jeff Bezos has most of his wealth in Amazon stock partly because he perceives Amazon stock as better than cash. (Which is a very good analysis. Even a huge crash in stock value would still outperform cash by a huge margin over time.)

If these assets were very risky or likely to cause a portfolio to never grow, the rich would absolutely not be utilizing them as much.

Are they? If you can't afford to own stock, you're probably much more vulnerable to the secondary impacts of a stock market crisis (losing one's job, etc).

I'd rather have a big portfolio that could go to zero than nothing at all.

Another perspective: by owning your house, you are vulnerable to a risk of fire, or the house market crashing.

Everyone should give me ownership of their house so that I can kindly take care or this terrible risk on their behalf.

This is ridiculously privileged pov to have

when the market falls it always recovers fast, so not a concern.