In chapter two, how does Greene establish a deep-seated religious faith on the part of common citizens?

In another part of town a mother is reading to her children, two girls and a boy. She is telling them the story of a young Mexican boy named Juan, a very holy boy who grows up to be a martyr, killed honorably for his faith in Christ. The children are infatuated with the story, and the girls ask if the man will become a saint, and their mother tells them he will one day.