A good and tough question. Remember that Ovid was writing for readers who would likely know the core stories he was telling, and so they'd be able to fill in the background when he just sketches a bit of the story, as he does here. To see this, you'd need to recognize that Lycaon served Zeus a meal where the meat was, well, human. Zeus rejected it, disgusted, and punished him fiercely, turning him into a wolf.
What this says about Greek religion is mostly that the rejection of human sacrifice marks a major turning point in both ethical action expected of humans and in the nature of sacrifice one makes to the gods. To kill humans is to become inhuman, in this case literally. It also marks a kind of psychological savvy that marks Greek myth, in that it gives us a metaphor for the killer: the wolf, the lone wolf who savages a pack he should protect.