@Buentello-
I'm not exactly sure why other artists remained anonymous, but most art (if not all) was performed for churches, so people thought it morally wrong to praise an artist rather than just praising God. The artists made artwork worshiping God and the Saints, so the subject matter was praised and NOT the artist. The artist worked for God, that is why they painted him and scenes from the Bible. It was their job to serve him.
Thanks!