...so how, exactly, is a billionaire supposed to get to his hideaway? Call an uber? To the airport to board his private jet? If it were even possible to launch a jet under such circumstances, why wouldn't the pilot have already grabbed his family (or a few stewardess) and and flown off to the hideaway himself?
Even if our Billionaire somehow gets to his his fortress, are his private security guards going to let him in? What, exactly, is he going to pay them with that is more valuable than what they already are occupying?
He can stand outside and yell all he wants about how they must "respect his authoritah", but any institution which gave him "authoritah" is gone.
I guess if you are a billionaire, it's easy to forget that the only reason we even have billionaires is that we believe they benefit all of us more than they are costing us. And in the event of a societal collapse, that would be manifestly untrue. To think that any of the rest of us would still just grant them all kinds of privileges after they had so incredibly misused the privileges they were granted is just the height of hubris.
Without an uncollapsed society, there would be no billionaires, anymore than there would be husbands without marriage.