Final answer:
The Roman Empire's extensive infrastructure, such as roads and safe travel, the Jewish Diaspora, and common languages like Latin and Greek contributed to the spread of Christianity.
Step-by-step explanation:
The Roman Empire facilitated the diffusion of Christianity through its extensive infrastructure, political changes, and the strategic positions of the Eastern and Western Empires. Roman roads allowed for easier travel and communication across the empire, creating a network through which Christianity could spread. Security of sea and land travel ensured that missionaries could traverse the empire safely to preach the Christian faith.
The Jewish Diaspora also played a significant role, as dispersed Jewish communities became points of contact through which Christianity reached new areas. With the Empire's common languages, Latin and Greek, the Christian message was accessible to a broad population. The acceptance of Christianity by emperors, especially Constantine, provided an imperial endorsement that furthered the religion's legitimacy and reach throughout Roman society.
As the Western Roman Empire faced societal disruptions and eventual collapse, the structure of the Church remained intact. During the third through the seventh centuries CE, the rise of Christianity and subsequent policies by Christian emperors moved the empire towards monotheism. This shift had profound implications for Roman society, as pagan worship was progressively neglected, and the Byzantine Empire maintained order focusing on the Christian population.