> (Though over in America, most of the historic grand mansions are now tourist attractions, for lack of heirs with the wealth and interest in maintaining them.)

Part of this is that the "old money" tended to withdraw from public life after the Great Depression when they decided infamy was a serious liability.

That's why one struggles to name any of the living heirs of the big names of that era, who are absolutely still filthy stinking rich, while newbies like Musk, everyone knows. The culture of what Fussell calls the "top out-of-sight" is to remain sufficiently anonymous that nobody knows their given names unless one goes looking (and even then, it may be hard to find much trace of them). A bunch of them don't show up on any of those "richest" lists not because they couldn't rank, but because you effectively have to opt-in to those, for enough of your wealth to be traceable without great effort to get counted.

Owning a highly-visible Newport mansion could well be a mark of poor taste, among that set.

They still have their grand houses, they just may not (though, may) be in the Georgian or Neoclassical style or whatever, and they're probably not visible (from remotely close-up, at any rate) from any public road. Drive minor highways in the right parts of the country and look for nice (though, not necessarily imposing or impressive) gates leading into what looks like a simple, wooded lot with an unremarkable, perhaps even gravel, drive that immediately disappears into the trees, and you've probably found one, and they're all over the place... plus their families will usually own plenty of extremely nice, but not flashy, well-located houses and condos and such in more-populated areas.