all the pagan godman myths came true centuries or millenia after they were propogated.
No, I don't think that follows from what I wrote. What I am saying depends on how you define "mythology." The colloquial meaning of "myth" is just something that is not true. But "mythology" has another meaning.
Probably the best explanation I have seen comes from the authorized biography of J.R.R. Tolkien:
"When Lewis and Tolkien had first met, Lewis was beginning to perceive the inadequacy of the agnosticism into which he had lapsed, having previously discarded any remnants of childhood Christianity. By the summer of 1929 he had renounced agnosticism and professed himself a theist, believing in the existence of God but denying the claims of Christianity. Essentially this was his position when, in September 1931, he had the discussion with Tolkien and their mutual friend, Hugo Dyson, which was destined to have a revolutionary impact on his life. After dinner the three men went for a walk and discussed the nature and purpose of myth. Lewis explained that he felt the power of myths but that they were ultimately untrue. As he expressed it to Tolkien, myths were 'lies and therefore worthless, even though breathed through silver.'
"No," Tolkien replied, "They are not lies."
"Tolkien argued that, far from being lies, myths were the best way of conveying truths which would otherwise be inexpressible. We have come from God and inevitably the myths woven by us, though they contain error, reflect a splintered fragment of the true light, the eternal truth that is with God. Myths may be misguided, but they steer however shakily toward the true harbor, whereas materialistic 'progress' leads only to the abyss and to the power of evil.
"Building on this philosophy of myth, Tolkien and Dyson went on to express their belief that the story of Christ was simply a true myth: a myth that works in the same way as the others, but a myth that really happened. Whereas pagan myths revealed fragments of eternal truth through the words of poets, the True Myth of Christianity revealed the whole truth through the Word himself. The poets of pagan antiquity told their story with words, but God, the omnipotent Poet, told the True Story with facts -- weaving his tale with the actions of real men in actual history.
"Tolkien's arguments had an indelible effect on Lewis. The edifice of his unbelief crumbled and the foundations of his Christianity were laid. Twelve days later Lewis wrote to a friend that he had 'just passed on from believing in God to definitely believing in Christ -- in Christianity. ... My long night talk with Dyson and Tolkien had a good deal to do with it.' "
So Lewis, an agnostic, came to be one of the greatest and most read Christian theologians of the 20th century.