The question “what happened?” is forced on us by the realization of how remarkable this phenomenon really was. Christianity began in obscurity. Its putative founder was executed and its first adherents scattered in fear and confusion. Its first missionaries were commoners, whose message appeared as nonsense to the sophisticated. With some exception, its chief appeal was to the outcast and marginal elements of society, finding significant numbers of converts among transients, slaves and women. From the first, it was violently persecuted. Yet, in the course of four centuries, Christianity became the dominant religious force of the Hellenistic culture. It swept all before it, becoming the established cult of the empire that had sought to extirpate it, the very form of wisdom for the sages who had reviled it, a movement with such resilient and universal embrace that it gathered all the charms of its cultic and philosophical rivals into a triumphant procession, in the end securing the allegiance of the cultured, the rich and the powerful.
~Luke Timothy Johnson, The Writings of the New Testament.
Amen to that!!