Egypt was a hotbed of religious controversy throughout the Roman period. The large Jewish community and their interaction with the Greeks in Alexandria (which was, to all intents and purposes a Greek city) led to a number of incidents from the early Empire throughout the principate. The coming of Christianity added another dimension and George, the bishop who replaced Athanasius in the mid 4th Century was lynched by a mob of Alexandrians. These are just a few examples off the top of my head. It is worth also denoting a difference between violence in Alexandria and violence in the rest of Egypt. The reason why so much recorded is probably a reflection on the sources you are citing. It would be worth checking their background and reasons why they may be reporting violence.