In the case of Jesus Christ, where virtually every detail of the story fits the mythic hero archetype, with nothing left over, no "secular," biographical data, so to speak, it becomes arbitrary to assert that there must have been a historical figure lying back of the myth.
Links in the gospels, e. g., with Herod the Great, Joseph Caiaphas, and Pontius Pilate, are so problematical on internal grounds that most critical scholars, never meaning to espouse Mythicism, reject these features of the story as legendary.
I am not trying to say that there was a single origin of the Christian savior Jesus Christ, and that origin is pure myth; rather, I am saying that there may indeed have been such a myth, and that if so, it eventually flowed together with other Jesus images, some one of which may actually have been based on a historical Jesus the Nazorean.