The only remotely plausible version of this scenario that I can think of is a world where Christianity spends another several centuries without much institutional power in Western civilization - that is, a world where Constantine is never born or converts to another faith and where the Roman Empire or any successor state or states do not make Christianity the state religion for another few centuries. Of course, Christianity and Christians would still exist, and other, smaller states may still designate some version of the faith as their state religion, including Armenia, Ethiopia, and perhaps a few Germanic kingdoms at the periphery of the Roman world.