The Fall of the Pagans and the Origins of Medieval Christianity

Why did pagan Rome, which had a history of tolerating other faiths, clash with early Christians? What was it like, under Roman law, to be a Jew or a Christian? What led to the great persecutions of Christians? Above all else, how did Christianity ultimately achieve dominance in the Roman Empire, eclipsing paganism in one of the most influential turning points in the history of Western civilization?