Christians believed the world to be spherical from the very beginning as this was established as a part of classical science (natural philosophy as it was known). While there were some natural philosophers who posited a heliocentric view of the universe, and even suggested that stars were other Suns with planets around them, this was considered to be a crackpot barking mad theory at the time. Geocentrism was primarily a scientific mistake regarding the construction of the universe rather a mistake of religious doctrine.
Come all ye faithful joyful and triumphant.
