Let me tell you.
Religion marked a new era for the Roman Empire. It paved the way for a new sort of political and social elite as well as reversed much of what was accomplished socially and politically by the pagan rulers prior to Constantine.
After the Council of Nicaea, which was the first ecumenical council regarding the theology of the Holy Trinity, the role of Bishop became a much more prominent political power. In fact, this council’s decision shaped what we know of Orthodox Christianity today. It was decided there that Christ was not God’s creation, but rather a part of God Himself. After this council, clergymen grew to become key elements of the imperial power structure.

None would have been possible were it not for the Edict of Milan, established by Constantine and Licinius - an edict which made it lawful to practice Christianity (and really, any religion) and enforced tolerance throughout the entirety of the Empire. However, it did pose a problem during the Donatist Schism in 314.
All this religious freedom was just too much for some people!

Constantine’s role as a religious figurehead went beyond establishing councils and creating edicts. After converting to Christianity, Constantine began to insert his theology into his empire. He built churches in Jerusalem - the most prominent of which being the Church of the Holy Sepulchre. He also had Christian buildings built in Rome and Constantinople, the city he had built as a personal capitol run by a senate of its own.
Also, while Constantine allowed for pagan temples to be built, he placed important restrictions on them. He even went so far as to allow imperial cult temples to be built in honor of his family as long as no blood sacrifices were performed there (a direct influence of his conversion to Christianity, since Christ was viewed as the last blood sacrifice.)

Christians continued to be a minority, but at least they were a privileged one! They were no longer in danger of being killed or having their land taken away from them. In fact, in a sense, Christianity became the thing to do. Clergymen were legitimized and granted immunity from taxation. Christian alms were seen often as a direct road to public honors, so many people converted to Christianity in order to gain political favor in their cities and were exempt from certain local duties.
The Chi Rho, Christ’s monogram, even became the symbol of the Roman military. Constantine’s deciding battle against Maxentius at the Milvian Bridge changed the face of the army entirely. As reported by historians present at the time, Constantine had a dream in which he encountered this symbol and was told “in hoc signo vinces,” or “by this sign you shall conquer.” Although this did not necessarily mark Constantine’s conversion to Christianity, it certainly was an important milestone.
Hey. Thanks for helping me study.
