The Qing Conquest of China
Weakened by famine, cold, and rebellion during the global crisis of the 1600s, China's Ming dynasty collapsed — the last emperor hanged himself on a hill behind the palace — and Manchu armies from the northeast swept in to found the Qing, the last imperial dynasty. A foreign minority of perhaps a million ruled over a hundred million Chinese for nearly three centuries by adopting Chinese governance wholesale while enforcing visible marks of submission. It is the dynastic cycle turning once more: a regime loses the Mandate of Heaven, and whoever restores order claims it.
Hardship plus a sudden opening (weak state, lost war, fiscal collapse) lets those who bear it overthrow the order — usually installing a new elite.