Why do you think Our Lord, the Son of God, decided to become man under the rule of the Roman Empire? Why was it Rome that crucified Him?
Out of all the periods of human history, why did God determine from all eternity that He should become man as a subject of imperial Rome during the pax Romana, which lets remember had only been instituted by Emperor Caesar Augustus in the year BC 27? Christ’s birth was perfectly timed during the middle of the reign of the Empire’s first ruler, a period of unprecedented peace, prosperity and stability for the world of classical antiquity.
Dante had a very ingenious, if controversial, answer to this question in his De Monarchia:
The Roman Empire eventually embraced Christianity as the state religion under Theodosius (around a century after Constantine became the first emperor to embrace the Faith as his personal religion), as we all know. This cannot have been coincidental.
In the West, the reconstituted Holy Roman Empire continued this legacy until it was dissolved in 1806, while in the East the Byzantine Empire carried the legacy of Rome until its dissolution in the fifteenth century. Christianity became synonymous with Rome, in time, and remains so today with our Holy Father the Roman Pontiff.