How did christianity spread throughout the roman empire, and what were the consequences?

At first it was considered a sect and it was prohibited and believers were prosecuted and often murdered, tortured, punished in cruel ways, or anything similar. It spread fast, however, since many people were poor and dissatisfied with the Roman empire and found comfort in such a religion that supported peace and love. Eventually, they were allowed to practice freely, and after a while it even became the official religion of the empire.

The answer is installation.