...Jesus was not the son of God. So his view of the diety being inconsistant with the old testament need not be explained at all.

From my agnostic point of view, and assuming there's a God who likes to keep us informed about Him, from time to time:

Maybe God's message is tailored to the people and the times. The old-testament Jews were not culturally capable of embracing the peace and love message of Christianity. Maybe Christianity was necessary because it was capable of conquering the Roman empire as Judaism was not. Maybe Islam was necessary because the Arabs were not culturally capable of embracing either Judaism or Christianity.

This would also explain the old-testament's view of creation (try explaining the big bang to an illiterate shepard, some time).

Nah!!!