You seem to have missed the point by a mile: who determines what is a core teaching? The Council of Nicea did based entirely on their own agenda, and not the teachings of Christ.

The fact that other Gospels don't talk about Jesus in the same way is not proof they are fake, but why they are "apocryphal." They don't depict Jesus in the same way! They don't reinforce the Nicean Creed. If there was any concern about inconsistency, Luke and Matthew would not have been included since the one contradicts the Nativity story of the other.

And of course you would bring Satan into this, and claim the books are tools of evil. That's what an unquestioning believer does when the faith (as they have been instructed by their appointed leaders) is contradicted.

That, and books are burned and heretics murdered. And so the faith continues, and the institution retains its monopoly over the followers. Social control, mind control, and violence to back it up. The history of the Church.