The Christian symbolism present has proven to be very prominent in The Lion, the Witch and the Wardrobe. There is no doubt the the author, C. S. Lewis had Christian values and that they came through in his writing. However Lewis said that he did not intend to write a Christian allegory for children, but rather that he set out to write a story for children and the Christian symbols simply developed as the story did (Higgins, "Allegory in C. S. Lewis' The Lion, the Witch and the Wardrobe"). Lewis stated that the story "all began with a picture of a Faun carrying an umbrella and parcels in a snowy wood" (Gleghorn, “The Lion, the Witch and the Wardrobe: Reflections on Its Meaning.”). The two images Lewis began the story with are not even any of the symbols of Christianity found in the book so it is clear that Lewis did not write the book with the intent of being symbolic of Christianity.
It is likely that Christianity came through the writings of Lewis because it was so deeply rooted in his own beliefs. He had written so many Christian books by the time he wrote The Lion, the Witch and the Wardrobe that his Christian values wove themselves into his story almost unintentionally (Complete Works of C. S. Lewis).