Yes, everyone who works on the bunker will know about it; and all these billionaires are trying to build their survivalist camps but dont actually consider any of the easily/practically broken parts of society they implicitly rely on.

Realistically, society we know it won't survive if it dwindles to beneath a couple of millions.

yeah but also realistically if you have the money you don't build a bunker, you build a pseudo military installation, and ex military is where you find your "handymen" to take care of "housekeeping." of course, your ex military pals should be consulted regarding real estate because even here its location location location.

As we know it, yes, but society in general will last until there's less than 2 people per kilometer or so