Hmmm? I can't think of a post that has addressed this issue. There are many observations and conjectures that can be derived from the religious aspect of the GF films.

From a Catholic standpoint, the Corleones were not devout Catholics (by the films depiction). In the book, Mama Corleone and later Kay are devout, prayful Catholics. But the religious aspect of the film provides a wonderful contrast and hypocrisy of the Corleone family. The obvious ones are no doubt the Baptism and murders of the Five Families. Catholic sacremental celebrations provide the backdrop for several scenes; in GF the Wedding of Connie and Carlo (although not in the church, but the priest is there), the Wedding in Sicily, the Baptism of Michael Rizzi. In GF II the Confirmation party of Anthony and in GF III the Commendatore award to Michael, all the Vatican stuff....the GF triology finds itself associated with Catholic Church ceremony. Why?

As a practicing Catholic, from a practical viewpoint I see religion for some people as an insurance policy and a cultural tradition. They better stay close to the church...just in case AND, the sacraments of the church (Baptism, Communion, Confirmation, Holy Matrimony, etc.) are a cultural experience. You do it because your mother and father did it and their mother and father, etc. Too often the party is the focal point and not the Sacrament. For the GF triology the Catholic traditions enrich the story. They provide a stark contrast between good and evil. And they provide the hypocrisy that fuels human interest in the story and characters. Religion is as much a part of the trilogy as murder and revenge. Relgion helps form the psyche of the characters.