Don't most of them have prepper level bunkers on large parcels of property, a private jet flight away in case things go truly south?

Yeah but compared to the value they have in equities that are active companies, employing people, and generating value, these underground bunkers are small.

If you have money you generally don't want it to sit around and depreciate instead of investing into real-estate, private equity, etc. directly or indirectly.

Possibly, but those are irrelevant sums compared to their total wealth.