A.D. 328 was the official consecratio of the new capital of Constantinople, the symbol of the new direction in which Constantine was taking the Roman empire. Constantine had planned it for some time, and construction had actually been proceeding for a couple of years. Now, it was official. Constantine rejected the old capital of Rome, and indeed, had always neglected it. Four years later, the bread distributions that had been a staple of Rome were transferred to Constantinople; the grain revenues that had supported Rome for so long now flowed in a different direction, just as the sources for that revenue began to dry up (quite literally, the canal system in the Fayyum was clogging up from neglect).
Indications of Constantine's new direction could be seen from a number of items.
In A.D. 311 Galerius issued an edict of toleration in the Eastern Roman Empire which stopped the active persecution of Christians. In A.D. 313 Constantine made Christianity legal. This is sometimes known as Constantine's edict of tolerance, but it turns out not to have been so tolerant. In 324, in the Egyptian city of Panopolis, Horion, son of Horion, applied for the familial post of prophet of the temple of Min. Constantine's government, however, rejected the application, and forced the whole family to relinquish their ancestral occupation (and the revenues) and find employment elsewhere. (The story is told in this book.) Christianity might be tolerated but the priesthood of Min would not be.
Actually, even Christianity would not be tolerated. Philosophical differences in the church of Alexandria caused a division in the Church. Constantine decided to settle the dispute, even though he was neither a philosopher nor a Christian, and did not really know anything about the subject. As a result of Constantine's meeting in A.D. 325, half of the Christians were condemned to persecution by their fellow Christians. The Christian world was also burdened with having to figure out and explain a poorly-thought-out and incoherent philosophical term.
Eusebius, a partisan of Constantine and his beneficiary, writes of Constantine in glowing terms, as though Constantine were the greatest thing to ever happen to Christianity, and had single-handedly ushered in the millennium. Alas, it did not prove to be such.