England lost its status as “a reserve currency “ to us slowly over time until they became completely irrelevant in the 70’s which many Britains remember as hard times with many not even able to afford heat. As their currency became more reliable again it once more is a currency of interest making lives easier in that region.
Before England
France had a reserve currency with much of the world, their influence was slowly lost ending in war upheaval and pestilence.
Both of the above survived, nobody keeps reserve status forever, so the nightmare scenario plays out relatively often, play stupid games win stupid prizes.
You would think humanity would become more intelligent over hundreds of years but the cycles of wars, financial collapse, democratic collapse and housing formation follow moderately long but predictable cycles.
At the end of the day we are animals that follow predictable build bust patterns every 80 years or so.