How was the story of Exodus passed on accurately?

Some might question it that this kind of colossal story would be able to pass on accurately via oral tradition: for example older men telling this story to others among his own tribe Beside the fire. My original intent was to ask that how is it possible that exodus story could be passed on to the next generation so accurately? Some might say that exodus story is a myth, because no-one can pass on this story so accurately as it is written in the Bible.