Lol in which world have you been living? Don't you see all companies, monopolies or not, died in Venezuela? Or any country that got destroyed.
The Roman Empire left nothing, only ruins.
Germany, China, Russia.. All those had FIAT collapse.. Do you think they lost their internal monopolies?
Do you think the Roman empire havent kept their weath after their fiat got destroyed? They turned into the Vatican
Since economy is not a closed system, you cant expect value doesnt transfer if a specific fiat is destroyed.