come on rich.  the greatest works of art?  insomuch as the church appropriated and controlled the money and power for as long as possible, sure, they were the only game in town for many artists.
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architecture?  The great cathedrals were the ancient equivalent of showing off how much power the church had.  Like a bank or business person building the tallest building.  If you actually think it has anything to do with a belief in a diety then you need more than just a course in logic