You can say the same thing about Game of Thrones.
There really was a wall that kept out the northern Barbarians. There really was a great chain constructed in a harbour to destroy attacking ships. That doesn't mean white walkers are real though.
The Bible is an example of accounts of some real historical events (for credibility) being mixed up with folk stories, while at the same time skewing facts to promote the views of the authors.
For instance, there is a real salt formation that looks a little bit like a woman looking over a lake, that clearly inspired the story of the destruction of Sodom and Gomorrah. The problem is it's way too big to be an actual woman who got turned into salt, but you can see how the myth developed over time, eventually becoming turned into 'history' cough

, by the authors of the Old Testament.
A similar thing happens where the Bible talks about 'the beast' coming from the sea, but it's not talking about the devil, it's talking about the Roman invaders. It's worded that way for anti-Roman propaganda purposes... and very effective it was too.