Not a history scholar but wasn’t it too much diversity that dropped the Roman Empire?
https://www.maier-files.com/the-euphrates-flowed-into-the-tiber/
...[early 2nd century AD Latin poet] Juvenal, had complained of the Syrian “Orontes” river “flowing into the Tiber,” a metaphor for people of Chaldean—i.e., Babylonian—extraction having “flowed” into the bloodlines of the ancient Roman stock: “These dregs call themselves Greeks,” he complains, “but how small a portion is from Greece; the River Orontes has long flowed into the Tiber.”...