Why did the number of Christians go from zero in the year zero to become the numerical majority of persons in the Roman world by about the year 350? How does one account for its dramatic success?
Many Christians themselves like to answer that question by appealing to the way Christian martyrdoms inspired the admiration of others, or to the power of witnesses who persuaded many that Jesus really had been raised from the dead. It was the miraculous work of God against all human odds that brought Christianity to the top.
A more plausible reason?
But would it make more sense if the reason was that Christianity itself encapsulated all the highest values of the Roman world as we find them expressed in their pagan traditional literature and stories. What if it was a religion that was increasingly seen as the epitome of what most people came to recognize as all that was good and noble in their pagan traditions?
The opening question is posed by Professor of Religion Gregory J. Riley and the answer he submits to it is:
It was the appeal of the early Church to the wider Greco-Roman society that fueled its rise, and that appeal was very much a result of its success in modeling the ideals of the culture as a whole. The early Christians imitated and copied the fundamental values found in the literature and stories of its wider culture as it formed its self-image and presented itself to the world. . . .
Christianity took hold in the empire as no foreign cult could (for example, Judaism, the Isis cult, and Mithraism) precisely because it was not foreign, but an expression and imitation of the best the empire had to offer.
(Riley, G. J. (2001) Mimesis of Classical Ideals in the Second Christian Century. In MacDonald, D. R. (Ed.) Mimesis and Intertextuality in Antiquity and Christianity (pp. 91-103). Harrisburg, Pa: Trinity Press International.)
Rick has posted another constructive response, 
