They will, however, have trouble stopping those guards from turning on them, once the collapse of society renders their wealth meaningless.
I wouldn’t be so sure. They wouldn’t only have monetary wealth, and o top of that some people are incredibly eager to just believe and serve others who they say they should be in charge. Aristocracies were essentially built on top of the idea that some people just decided they were better than others and deserved to be on top, and everybody mainly just went along with it