Sometime in the winter of 39/40 the Greek population of Jamnia in Judea erected an altar to the imperial cult (worship of the emperor) and the resident Jews promptly tore it down, resulting in serious communal rioting.
This proposal struck at the very heart of the religion of the Jews who were an important element of the population and business sector of most cities throughout the empire (as shown in The Acts of the Apostles and attested by Roman historians).
It appears that there were no overt threats of violence, though it was clearly in the wind, and the harvest (40) was being neglected already, which could bring famine to Tyre and Sidon and other neighbouring areas (see Acts 12:20-24 just four years later).
[3] All agree that the one man from whom Caligula would take advice, Herod Agrippa, arrived back in Rome previously unaware of what was brewing and persuaded him to offer to rescind the temple order in exchange for Jewish promises not to interfere with the imperial cult outside of Jerusalem.
[4] Claudius became the new emperor immediately, aided by Agrippa (the Herodian family were always able to play both sides against the middle) who was rewarded with sovereignty over Judea and Samaria in addition to his existing rule, and Petronius was recalled to Rome.