Quote from : The Vampire Lestat Book

As the Roman Empire came to its close, all the old gods of the pagan world were seen as demons by the Christians who rose. It was useless to tell them as the centuries passed that their Christ was but another God of the Wood, dying and rising, as Dionysus or Osiris had done before him, and that the Virgin Mary was in fact the Good Mother again enshrined. Theirs was a new age of belief and conviction, and in it we became devils, detached from what they believed, as old knowledge was forgotten or misunderstood.