Not so. In the short story, there was a group known as the Cult which used their scriptures to predict the Nightfall itself. While they were in fact correct, they didn't want to preserve civilization...that was the goal of a group of scientists.
Reread the story. Both groups were maintaining continuity, but from opposite viewpoints. The Church had records going back several cycles.
Also the original short story is different from the expanded novel.
It wasn’t fundamentally all that different from the current situation where both science and the Bible seek to explain everything. Odd convergences happen...