What Abdul Goatherd said.Give a specific reference to that please, I'd be interested to hear it. I'm more or less familiar with the modern Bible, and I can't see where that shows up anywhere.
Exodus is extremely implausible history. The theology I leave up to you (personally I have a hard time crediting a story in which God kills children because of something their parents' ruler did). But as a historical source, Exodus is not confirmed by any other source and contradicts the archeology of Israel. There may well have been movements of individuals and tribes from Sinai into Canaan but entire peoples on the move as depicted in Exodus should leave an archeological trace. There isn't one, Israelite culture as a whole developed in Canaan without interruption. There was no conquest either, as described in the book of Joshua. Various towns were destroyed at different times, consistent with normal levels of infighting. Egyptian overlordship over the ancestors of the Israelites is historically well-attested (before the Bronze Age Collapse) but it took place in what is now Israel because Egypt extended its influence there.Except the Exodus is about an entire people fleeing from another kingdom and eventually conquering and founding their own. Which is historically quite plausible since this happened several times throughout history. Even if you take the stories of literal miracles with a grain of salt, the fundamental narrative of the Exodus is pretty solid. We know that there's a strong Egyptian inflience in Hebrew society and technology. We know that this kind of migration was very common in the Middle East throughout history, from the Sea Peoples to the Phoenecians to the Greeks to the Turks, there's a vast history of exactly the kind of migration as the Hebrews describe.
Effectively the deep story of the Exodus is an Egyptian nation that exploited the Hebrew people with slavery and forced labor, then through a series of catastrophes lost control of their Hebrew slaves, who escaped, lived for a period of time as a nomadic people, and invaded and conquered a space for themselves in the Middle East. Is that really so different from what the Turks did centuries later?
Now personally as a Christian, I believe in the mythological stuff too, but that certainly doesn't change the histprical significance of plausibility of the story of Exodus. Discussion of this Biblical book belongs in a historical forum
Of course, if the story appears exaggerated or even invented, one would ask why that was done. The answer is in the Documentary hypothesis mentioned by Abdul. It says different parts of the Bible were composed or edited at different times to suit the needs of the editors. In the case of Exodus and Joshua the decisive edit coincides with the return of Jewish elites from Babylonian exile, and the story helped justify their rule over the population that remained in Judea.