Explanation: Constantine was the first Christian Emperor of Rome. More than just a novelty, Constantine put great effort into converting Romans to the religion of peace! BY FORCE! (or, more specifically, the forceful suppression of pagan religious practices)

One notable aspect of this, along with the more autocratic-monarchic position of the Late Roman Empire, was a development of Roman Imperial ideology. Traditionally, the Roman Emperor was considered ‘just’ a magistrate of the Empire, which was an Imperium Sine Fine - an ‘Empire without end’, destined to rule the world because of the innate justice of its system (please ignore all the injustices of the system). “One Empire”, but many gods, and the Emperor was only a part of a greater system, not even indispensable.

The adoption of Christianity and a more monarchic mindset at around the same time resulted in the idea that Emperor, God, and Empire were all connected - as there was one, all-powerful ruler in the heavens, so too should there be one all-powerful ruler on earth, with one all-powerful state transmitting his commands; all in harmony with each other. One God, one Empire, one Emperor!