Saename:
My comment above was not about Constantine's pre-conversion status but about the likely reason why Constantine promoted the Paulines out of all the other conflicting voices of early Christianity, after his conversion.
According to:
http://www.jwstudies.com/Why_Does_WTS_Accept_Christendoms_Scriptures.pdf
Among the early Christianities were the Ebonites, Marcionites, Montanists, Gnostics, Docetists, Valentinians, Sabellianists and others who considered themselves to be true followers of Jesus. But the group that ultimately triumphed were the Paulines who became known as Orthodox - their opponents were branded as heretics.
The dominance of the Pauline sect was recognized and spread by Emperor Constantine and its beliefs were further influenced by Emperor Theodosius.
The Church Fathers and the churches that ultimately delivered a list (canon) of sacred Scriptures, could not be described to be in any way in complete harmony with one another. They added to the cacophony of conflicting ideas. The nation that consistently sought for harmony and unity imposed its will upon this babble of conflicting ideas. It became involved in the internal disharmonies that existed within the maelstrom of conflicting Christian ideas and drove them.
That nation was the city-state of Rome.
The division among the Christians grew until Emperor Constantine in 325 CE called a general Council, in order to heal the rifts.
The men who strove for harmony, even to the point of deciding doctrine, were Constantine and Theodosius. They promoted Christianity and they promoted only one of its many voices: the Paulines.
The outcome includes the rejection of Arianism (Theodosius in 381 CE) and ultimately the list of sacred Scriptures, the New Testament.
If Constantine had installed a different form of Christianity, then the list of sacred Scriptures, the teachings and the practices would have been completely different.
The Christianity which Constantine joined was that proposed by the successors of the Apostle Paul. Other forms existed, with at least Marcion operating from Rome for a while. Constantine caused the survival of Christianity, having made it the formally recognized state religion and the recognized format was Paul's religion. Constantine became closely involved in it, bringing with him the Roman desire for harmony and unity. For that reason, he instituted the church-wide Council at Nicea, its task being the setting of the date for Easter.
A few decades after Constantine instituted Christianity, the Roman desire for harmony and unity, this time within the Church, manifested itself in 381 CE when Emperor Theodosius instructed that Arianism was not acceptable - the long and detailed philosophical discussions within the church on the nature of Christ were resolved by imperial decree.