Would they always need earth to be habitable?
Because if they somehow managed to terraform and colonise another planet like mars, wouldnt they just make earth so uninhabitable that the rest of us would be forced to go where they are? (Prolly as slaves)
Where would the billions come from?
Money is nothing if there are no people who honor it.
Additionally, the people in that class are outright incapable of maintaining their aspirations without hiring others with their money to be spent in society as an incentive. Even if mass automation occured, a single event of system failure or being presented with a new situation that they cannot figure out with their skillset could result in death or being stranded.
I believe this concept was already brought to light when that science fiction author was asked by UHNW investors how to set up a system where their bodyguards wouldn’t just kill/overthrow them and take over their doomsday compounds in the event of societal or ecological collapse (I guess both as well), and the author essentially said “be nice to them”.