Answer:Why was the Christian community something that people wanted to join? I think that only because at least certain parts of the early Christian mission were intent in creating new community, that only for that reason this movement was successful. Now what does it mean "new community?" Let me talk about this in two different levels. One was certainly that the message that was preached here promised gifts, spiritual gifts, to people that went beyond the everyday life experience and promised also immortality, a future life which would be liberation from sickness and from disease and from poverty, and individual isolation. There is a future for the individual. And the message of the possibility for a human being to be related to something that is beyond the powers of this world was certainly one great attraction. But that alone would not have been enough. I think it's a very important spiritual-religious factor. But it would not have been enough, because, in spite of all the glories of the Roman Empire, people lived in the world in which there was inequality, there was great poverty on the one hand and immense wealth in the hands of a very few people. There were sickness and disease and there were no public health services, and doctors were expensive.
Now here's also the question of the inequality which Rome really reinforced through the Augustan system. Rome is a very strict hierarchical system, in which the emperor is at the pinnacle, all the way up and then all the blessings in the world that come to people come down from above. The emperor is the conduit to the divine world. And if you're at the bottom of that social pyramid, not a whole lot of things are coming down to you anymore. Slavery slowly diminished, but continued to exist.
Now the Christian community, as we have it particularly in the letters of Paul, begins with a formula that is a baptismal formula, which says in Christ there is neither Jew nor Greek, neither male nor female, neither slave nor free. This is a sociological formula that defines a new community. Here is a community that invites you, which makes you an equal with all other members of that community. Which does not give you any disadvantages. On the contrary, it gives even the lowliest slave personal dignity and status. Moreover, the commandment of love is decisive. That is, the care for each other becomes very important. People are taken out of an isolation. If they are hungry, they know where to go. If they are sick, there is an elder who will lay on hands to them to heal them.