I don't understand this. That is, if you have $1B, I think you'd be a lunatic to not spend $20M in "insurance". Why wouldn't you "prep"?
I'm not rich, but I live in rural Canada. So I have the possibility of being cut off from power, and during intense storms days or even weeks. I have 6 months of canned food, the logic being that I may have company, or I may need to care for my neighbours during time of need. And if there's no power (heat), your daily intake of food can double or triple.
So I buy canned food on sale, save money, and also have insurance. It's saving me money by buying in bulk on sale.
Do I think I will be cut off for weeks? No, not really. But it can happen, and yet this costs me nothing except pondering what I should do. It's just sensible. Just like when one buys insurance, you don't plan to have your house destroyed, but you buy house insurance, because it can happen.
So I really see no evidence of "knowing something will happen" or even "expecting it to", when I see someone with millions of dollars in spare cash, buying insurance.
In fact, if you have $1B, and no 'escape plan', what the hell is the money even for?! I'd think ensuring your future would be a big part of it a good use case, right?