One of the first things Constantine does, as emperor, is start persecuting other Christians. The Gnostic Christians are targeted...and other dualist Christians. Christians who don't have the Old Testament as part of their canon are targeted. The list of enemies goes on and on. There's a kind of internal purge of the church as one emperor ruling one empire tries to have this single church as part of the religious musculature of his vision of a renewed Rome. And it's with this theological vision in mind that Constantine not only helps the bishops to iron out a unitary policy of what a true Christian believes, but he also, interestingly, turns his attention to Jerusalem, and rebuilds Jerusalem just as a righteous king should do. But what Constantine does is take the city, which was something of a backwater, and he begins to build beautiful basilicas and architecturally ambitious projects in the city itself. The sacred space of the Temple Mount he abandons. It's not reclaimable. And what he does is [to] religiously relocate the center of gravity of the city around the places where Christ had suffered, where he had been buried, or where he [had] been raised. So that in the great basilicas that he built, Constantine has a new Jerusalem, that's splendid and beautiful and... his reputation as an imperial architect resonates with great figures in biblical history like David and Solomon. In a sense, Constantine is a non-apocalyptic Messiah for the church. ...
The bishops are terribly grateful for this kind of imperial attention. It's not the western Middle Ages. The lines of power are unambiguous. Constantine is absolutely the source of authority. And there's no question about that. But the bishops are able to take advantage of Constantine's mood and his curious intellectual interest in things like Christology and the Trinity and Church organization. They're able to have bibles copied at public expense. They are finally able to have public Christian architecture and big basilicas. So there's a comfortable symbiotic relationship between the empire and the church, one that, in a sense, is what defines the cultural powerhouse of Europe and the West."