The Russian Revolution
Battered by the slaughter of the First World War, mass hunger, and a discredited monarchy, Russia erupted — and in the chaos the Bolsheviks, a small, disciplined faction led by Lenin, seized power and built the world's first communist state. What began as a revolution of workers and soldiers hardened, under Stalin, into one of history's most total dictatorships. It is the revolutionary pattern's most common and bitter ending: hardship and an opening producing not freedom, but a new and harsher elite.
Hardship plus a sudden opening (weak state, lost war, fiscal collapse) lets those who bear it overthrow the order — usually installing a new elite.