The rise of christianity in the Roman Empire was different to that of medieval Europe.
In the Roman Empire, christians were persecuted at the beginning and very slowly increased the amount of people who believed in their god. However, as time passed, more and more people identified themselves as belonging to the christian religion.
In medieval Europe on the other hand, christianity became popular much faster, as there was not that much opposition, compared to the times of Roman empire.
Martin Luther. He ended up starting the Protestant reformation this way
