There is much evidence in the world that WWII actually took place. A writer using this factual evidence to write a fictional story about a war hero, is indeed correct that WWII took place but the story about the war hero is still fictional. One cannot claim that because of the first fact the second part of the story is also a fact. The same is also true of the ancient historic books. Even if it is about a real person the story would be colored by he opinion of the writer, a witness, or even by the memories of the person evolved. Memories are not reliable (another blog on that subject will follow later) and even testimonies are influenced by what the witness wants his/her audience to hear. The fact that we find the ruins of Jericho or the Tower of Babel does indeed prove that these places existed but it does not prove that the stories about them are correct. What made the walls of Jericho collapse? A trumpet call (supernatural interference) or an earthquake (a coincidental natural disaster during the siege)
The stories at that time were written by people with certain believes and opinions, just like what we experience in modern literature. We therefor conclude that although the historical background of these ancient books is proven to exist, it does not prove that the stories describing what happened at that time is the truth but is rather a fictional story woven into the narrative.