In 1860 BC, Ikūn-pî-Ištar, king of Isin in Sumer, received a very troubling prophecy: a great tragedy would befall the King, soon. So Ikūn-pî-Ištar had a genius idea: let's take some poor idiot, make him king, and then "rebel" against him and put him to death, satisfying the prophecy and leaving Ikūn-pî-Ištar unharmed. Ikūn-pî-Ištar picked the first lowly worker he found, a gardener named Enlil-bāni, and abdicated the throne in his favor. Ikūn-pî-Ištar then went off to eat a bowl of soup, which he promptly choked on and died. Enlil-bāni then refused to relinquish the throne and reigned for a relatively safe and prosperous 24 years, lowering taxes and rebuilding the city's temples and walls.
Source: History of the Ancient World by Susan Wise Bauer
Was it the Assyrians or just the Sumerians who had this tradition? Because in the Fall of Civilization podcast about Assyria, the host mentioned there is a tradition where the king makes a guy king for a month then kills him to appease slash "fool" the gods. Happened more than once. Also kinda strange how Enlil-bani managed to rule for 24 years, considering it's usually the powerful nobles / powerful families who command the armies and thus decide who gets to be king.
It later became more popular in Assyria, but this is iirc the first recorded instance of it happening.