Civilization just takes it as a given that the whole world was flooding. Then science came and you had geology and modern astrophysics, and time became well understood going back billions of years. So enlightened religious people, as a necessity, had to shed the magical elements of the Bible. A little known fact is that Thomas Jefferson did just that. There's something called the Jefferson Bible. It's not widely publicized because it sort of conflicts with certain people's ideas of what the founding fathers were.