Hyper-inflation does happen sometimes. What causes it?
An irresponsible central bank.I think that scenario is unlikely for dollars, because the Federal Reserve central bankers already have a lot of dollar-denominated wealth, so have a strong incentive to avoid hyperinflation.
Compare that to the Zimbabwe central banker, who is basically under the thumb of a dictator who most likely holds his wealth in foreign currencies. Their incentive is to squeeze as much wealth out of the economy before it collapses and they're deposed in the next coup.