You can buy the writting of Eusebius in Penguin classic. Roman Empire was not really christianized until 400. Even during the sack of Rome in 410 majority of population in the city was pagan. Christianity had the biggest appeal among barbarians and poor who could not associate themselves culturally and socially with the pagan Rome. The Greek speaking world that made about 40% of population when through deep cultural renewal and revolution where greek language rejuvenated especially among Christians. The greek culture, social structure, and political system did not suffered with a rejection of the Christians as did latin speaking western Roman Empire. Actually the Greek speakign, eastern Roman Empire associated themselves as the kingdom fo Jesus with Jesus being the highest apex of the state. Romanized West lacked such symbol and disintegrated between 406-476. It was not until the rise of the Frankish empire when the rulers started to use Jesus as the supreme governor and they rule within his blessing.
Constatine was a pragmatic ruler. He embraced Christianity as way to unify socially and politically divided empire. Constantine overruled ban on Jews in Jerusalem. Julian Apostate (+363) was the last pagan ruler who embraced multicultural Roman society. He also supported Jews and their return into Jerusalem, eliminated specific taxes on Jews and funded several synagogues. Julian believed that Jews can be counterbalance toward the Christianity that was taking hold within the Roman Empire.