Why were there so many religious pieces of art during the Medieval time period?

Medieval art illustrates the passionate interest and idealistic expression of the Christian and Catholic faith. Architectural designs and their interior décor showed avid expressions of the deep religious faith of the people of the Middle Ages

During the Middle Ages, art was more religious because it had a very religious influence from the church having such great power in the community. ... Art with biblical themes were popular in the Middle Ages because the artists were also focused on theology. Jesus and Mary were usually the main focus in most paintings.