Like many of the later Roman Emperors, Constantine was not Italian. In fact, he wasn’t even “Roman” except technically. He was arguably British. How he became Emperor of Rome and head of the Christian Church makes a wonderful story.
By the time Constantine was in his teens, there were routinely four “emperors” of the Roman Empire at any given time: two in the east and two in the west. The idea was that they would share power and balance one another’s dreams of supreme oppression. So, both in Rome and in one or another cities in what we would today call Turkey, there was generally a ruler called “Augustus”, and another called “Caesar”. One or the other was usually a general, and generally ruled from a tent at the head of his legions. It was a complicated system and it never worked especially well, but it was what it was.
The story goes that he never forgot his debt to the Christian God in winning him his empire, and so he immediately legalized the Church. On his deathbed, several years later, he is said to have been baptized, himself. In the meantime, having legalized the Church, he set out to figure out how he could make use of it. He was astounded to find that there were several competing versions of Christianity, and that they quarreled with one another pretty much constantly. Of most immediate concern to him was what became known as the “Arian” controversy, which threatened to split the newly legalized Church in two, just as it was becoming likely to survive.