how did the Christianity spread after 100AD?

A look at how the Gospel spread in the beginning - What were the
factors that allowed a persecuted faith to take over the Roman
Empire?
Depending upon the theological background, the answer to this
question (what were the factors that enabled a persecuted, minority
faith to take over the Roman Empire?) is extremely varied. A Yale
professor, Dr. Ramsey McMullen (a secular scholar), SHOCKED the
Christian world with his answer. You may be shocked as well!!