I don't think 3rd century Christians were comparing different accounts and selecting them on the basis of how well they would function as allegorical myths. I could be wrong, but as far as I know that is a modern invention, developed to reconcile the supernatural elements of scriptures with the naturalistic worldview that developed during the enlightenment. To understand the setting of early canonization, you have got to picture a world of persecution, faith and martyrdom that is hard for us to imagine in our liberal, secular and comfortable world.

I understand that the view of the Bible as a product of natural selection is a way to transpose the belief that it was not made through purely human forces to a philosophical system where all nonhuman forces are natural. However, the argument for relevance to modernity is severely weakened by this rebasing. It is not the present environment that determines the shape of the animal, but the historical environment, and while the survival of a species is a testament to its adaptation for the historical environment, it is not a testament to its adaptation for the present environment. Since the historical environment was a combination of true faith, and later illiberality, there is no reason to think that it should be adapted for the modern environment of the allegorical view and religious freedom. That is why I do not think the naturalistic view works as a justification for the providence of the scriptures.