I don’t believe any of Harry Potter really happened either, but that doesn’t mean I can arbitrarily claim the story is different from what it is.
to the extent that i am making a real point here, it is just that westerners should probably not find the idea of willing child sacrifice so bizarre/unbelievable when the common patriarch of judaism, christianity, and islam is portrayed as being totally devoted and willing in one of the faiths' most well known stories.