How global currencies work past, present, and future by Eichengreen has a good history of currencies (from a European perspective). There were a few times when there were multiple currencies being used, and the ones used were the ones related to the countries who had the largest trade networks / 'colonies'. Of course credit was used a lot as well over long distances so folks didn't have to lug things around (Debt: the first 5,000 years by Graeber). Various cities vied between each other for the most transactions and business; Capitals of capital by Cassis has a modern era history.

Before that, gold and silver were often used as lowest common denominators internationally. See The power of gold: the history of an obsession by Bernstein for that. However metals weren't used everywhere: e.g., China used paper currencies for many years, and giant rocks where used in Micronesia:

* https://en.wikipedia.org/wiki/Rai_stones

Money: the true story of a made-up thing by Goldstein has a good pop-history overview.

Power often didn't come into play for currency choice, and neither did things "implode" as opposed to a gradual shifting in preference amongst currency users.