Until now, the relatively quiet transition from traditional Graeco-Roman religion to Christianity has gone unexplained. In dialogue with James Rives and Jörg Rüpke, I argue that Christianity made better use than its religious competition of long-term trends in the Roman Empire, such as expanding literacy, the rejection of sacrifice, the movement toward monotheism, and the closing of the distance between gods and their faithful. The growing skepticism within the city elites regarding the credibility of its traditional religion, the decrease in investments in its material side, and the strength of the Christian organizations were additional factors together with contingent events, such as Constantine’s victory and his long rule.