They do believe in the bible but they're taught that some of the Old Testament stories were just that...stories.
I started off being Catholic with my father's remarriage when I was growing up, before I learned the gospel of the Bible and became a believer with the Bible for basis. I still thought the Bible was to be trusted before as a Catholic, though I heard hardly any direct teaching from Bible passages.
Why not believe there was a great sudden worldwide catastrophe to the world creating layers with fossilizing bodies, with a worldwide flood occurring and great deposits of sediment, yet believe accounts that this world was once long ago a snowball earth? Seeing great ages of many millions of years with gradual evolution involving natural processes is one interpretation of what remains.
