Despite centuries of persecution by Christians, a few hundred thousand people still cling to Greco-Roman paganism, either in small rural communities scattered across the Meditteranean or part of the community of "Hellenes" in Persia/Mesopotamia (OOC: Something akin to the Parsis of India), so, what if Greco-Roman paganism fully went extinct during the Christianization of the Roman Empire? What PODs could have resulted in a scenario where Greco-Roman paganism went extinct, then?
OOC: Basically a scenario where Greco-Roman paganism went the way of Zoroastrianism instead of fully dying out.