Why did Romans persecute Christians before Constantine I’s reign?

Before the reign of Constantine I, Romans persecuted Christians primarily because the faith was viewed as a threat to the stability and divine favor of the Roman Empire.12

The fundamental cause of persecution was the Christian refusal to worship the Roman gods and the emperor, whose favor was believed to protect the state. By rejecting these traditional rites, Christians were often blamed for natural disasters, military defeats, and economic crises, as they were seen to be provoking divine wrath.12

Other factors contributing to this hostility included:

• Social Distrust: Christians were often viewed with suspicion due to their detachment from public life, including their reluctance to serve in the military or hold state offices.12
• Misunderstandings: Rumors of secret vices, such as cannibalism and sexual promiscuity, circulated due to the private nature of the Eucharist and the Christian practice of referring to one another as "brother" or "sister".1
• Political Tension: The preaching of a "new king" was perceived as potentially revolutionary, and Christians were often seen as disrespectful toward ancestral customs.1

While early persecutions were often sporadic and local, later efforts—such as those under Decius and Diocletian—became systematic, empire-wide attempts to restore unity and divine protection through forced conformity.1