Because they have reached a position in society where they get whatever they want. Nothing to worry about - just throw some money at a problem and a lackey mak

Because they have reached a position in society where they get whatever they want. Nothing to worry about - just throw some money at a problem and a lackey makes it go away for you. But if there is a catastrophe/pandemic/war/flood/whatever they'd not be able to simply buy their way out of it like they can with pretty much everything in normal life that they can do today. Their startegy is buy a place (not just a property!) where they are largely in control of who comes there and what they do. Isolated islands obviously help with this because people won't be climbing over your fence like they wood on the mainland.