The Haitian Revolution
In France's richest colony, half a million enslaved people rose up, seized the Enlightenment's promise of universal rights that had been meant to exclude them, and — after defeating the armies of France, Britain, and Spain — founded Haiti, the first nation born of a successful slave revolt. It was the age of revolutions turned against the very powers that had coined it. Here, hardship plus an opening produced the most radical outcome of all: the enslaved making themselves free and sovereign.
Hardship plus a sudden opening (weak state, lost war, fiscal collapse) lets those who bear it overthrow the order — usually installing a new elite.