The highlighted statement is incorrect.
Actually It wasn't Constantine who made Christianity the state religion. He he tolerated Christian worship in his empire – the edict of Milan (313 AD). This gave no preferential treatment of Christians but put them on the same footing as pagans as regards taxes etc .
After Constantine the empire was at times split and at other times united. After Constantine I, the empire was again split in two with Constantius II in the east and Constantine II in the west.
Constantine II was followed by Constans I and then Constantius II (from the east) became emperor of the west as well.
He was followed by Julian the Apostate (a pagan) and he was followed by Jovian (both sole emperors).
Then in east Valens and Theodosius I; in the west Valentinian II , Gratian and Valentinun II. And Theodosius I
In 379 Theodosius I became Emperor of the East. In 380 he and Gratian (in the west) made Christianity the state religion – some 43 years and many Emperors after Constantine (6 in the east, 8 in the west). But after the death of Valentian in 392 there was an attempt to restore paganism until Theodosius swept in and took power in the west to unite the Empire.
Like I said I could not do it justice. But definitely and ultimately Christians and Christianity were given preferential treatment....but it was not an overnight thing...struggles....the preferred religion did ultimately became the Roman Empire.
The history of Rome is one thing but politics and culture of the Roman Empire is another.
As far as Emperor Constantine making Christianity the state religion, that is a loose term, but here ya go...
In 313 AD, the Emperor Constantine issued the Edict of Milan, which accepted Christianity: 10 years later, it had become the official religion of the Roman Empire.
In 313 Constantine and
Licinius announced "that it was proper that the Christians and all others should have liberty to follow that mode of religion which to each of them appeared best,"
Basically freedom of religion...Funny that the Greeks were the first to practice the concept of democracy. A good part of the Roman Empire was still Pagan....it was a logical choice not to declare war on them because it would have brought the Christians under the "gun" again.
Constantine the Great and Christianity - Wikipedia
Various Emperors contribute to continuing Christianity in the Roman Empire
State church of the Roman Empire - Wikipedia
Nothing happens like a light switch.
In 313 CE, the emperor Constantine issued the
Edict of Milan, which granted Christianity—as well as most other religions—legal status. While this was an important development in the history of Christianity, it was not a total replacement of traditional Roman beliefs with Christianity.
In 325, Constantine called the
Council of Nicaea, which was a gathering of Christian leaders to determine the formal—or
orthodox—beliefs of Christianity. The result of this council was the Nicene Creed, which laid out the agreed upon beliefs of the council.
In 380 CE, the emperor Theodosius issued the
Edict of Thessalonica, which made Christianity, specifically Nicene Christianity, the
official religion of the Roman Empire. Most other Christian sects were deemed heretical, lost their legal status, and had their properties confiscated by the Roman state.
Constantinople (330-1453) founded under the direction of Emperor Constantine was not only the largest and richest urban center in the Eastern Mediterranean Sea, it was jewel of Christendom. Dedicated to the advancement of Christianity in worship...study... schools and art.
And still this is just a thimble full of information.
