Well, the need for that incarnation, or that infusion of spirit and matter entailed that the material world had fallen from God's grace. The whole thing was neoplatonic. I think it's hard to talk of what's "alien" to Christianity because that religion is highly syncretistic. It combined Judaism with Greco-Roman dualism and with the dying and rising gods mytheme. The dualistic Gnosticism shows up in Paul and in the Gospel of John.

The problem is that some reason had to be found for why a righteous man like Jesus had to die in such a humiliating fashion. If he had died as a sacrifice to atone for our sins, that theology meant the world was in a fallen state, one that was controlled, then, by demonic powers which tempted us, proving our lack of faith.