Christianity

I don't understand the question. It does not compute. Before Jesus died, there were no vampires or zombies. People came back from the dead routinely. No reason, they were not vampires or zombies or anything else in particular, they were hallucinations, religious skullduggery, entertainers, and scam artist tools. After Jesus died, it became well known and commonly accepted that the ONLY person who came back from the dead was Jesus, so when people continued to come back from the dead, they had to be called something else besides 'humans coming back from the dead'.