The Crash of 1929
A decade of giddy speculation, much of it on borrowed money, ended when the American stock market collapsed — and the crash cascaded into the Great Depression, a global slump that threw a quarter of workers out of jobs and fed authoritarian movements around the world. It was mania and debt unwinding at once, the same curve as the 1720 bubbles. And its misery cashed out, again, as a political hunger for strongmen who promised to make it stop.
A speculative belief detaches asset prices from fundamentals; the belief breaks and prices collapse.