these kinds of apocalyptic speculations are hilarious: most of these billionaires couldn’t change a light bulb or boil a pot of water, and except for (maybe) close family, the so-called “loyalty” of any servants or minions wouldn’t last very long, esp. any armed “guards” ... also, they can have all the walled compounds they want, but sooner or later they’ll run out of some essential part, component, material or substance necessary to keep their cushy lifestyle intact ... survivors outside said compounds will devolve into warring tribes and a few surviving tribes will grow strong enough and desperate enough to invade said compounds ...
also when the USA falls other dominoes and they will find themselves without wealth. After if the USA no longer exists, your dollars are worthless
Or the rich boys security decides they are tired of being treated like crap and offs the rich boy and takes it all for himself. Some probably haven’t thought that far ahead, but some have and are probably considering AI to do their security work. We saw how that turned out in the Battlestar Galactica series why wouldn’t it do the same in real life.
Let them build their expensive tombs...