The Collapse of Paganism

Collapse of Paganism
Polytheistic paganism was widespread in the first and second century. What happened that caused the practices to essentially disappear by the mid fourth to fifth centuries?

Mani and Manicheanism
Major religion in the 4th through 7th centuries. Originated in the Sakkonett Persian empire. Foundational belief is there is only good and evil in the world, and this is the stage of an eternal battle between good (God) and evil (The Devil).