Why do you think so much of the art created in middle ages was religious?

The church commissioned the works through sponsors like the Medici and there were very few topics artistes could do beyond religious work. The people of the time were just learning to read after the printing press, but the church still used the religious symbols and stories to teach their people and this is reflected in the art produced, but if you look very carefully there are symbols in the paintings that reflect an idea or a philosophy. Michelangelo did paint the Neoplatonic thinking in his Sistine fresco showing man touching the hand of God. This basically said that man didn't need the church as a middle man between God and man.