Who were your 'first' Christians? I don't refer to the 12 Apostles but to the arc of early Christianity.
It is generally accepted that Christianity grew mainly due to pagan conversions.
Among Jews that was a rarity. Jews knew Judaism and knew their Messiah would be a great and powerful leader, not a common criminal cursed by God to die on a tree.
And what evidence are you basing this upon?
Because....
"... Christianity, in its earliest beginnings, is part of Judaism... it is a sect, among a number of varieties of Judaism in the Roman Empire. But it is also clear that at a certain point, they develop a consciousness which takes them outside of the social orb of Judaism. They're no longer part of the local Jewish community, they're a separate community, meeting in little household groups, all over the city. And, it's apparent, at least from the time of the Emperor Nero, that outsiders also view them as distinct. So that when Nero is looking for scapegoats upon whom to put blame for the fire in Rome in 64, he zeroes in on the Christians.
So, obviously they are recognized as a distinctive group. How did this happen? What is involved in their separation? The one thing I think we have to recognize is that it doesn't happen all at once. It does not happen in the same way in different places, nor does it happen at the same time. For example, as late as the 4th and 5th century, we have evidence of Christians still existing within Jewish communities, and we have evidence of members of Christian communities participating in Jewish festivals. The preacher of Antioch and later of Constantinople, John Chrysostom, complains in a series of eight sermons to his congregation, that "you must stop going to the Synagogue, you must not think that the Synagogue is a holier place than our churches are." This clearly indicates that the break between Judaism and Christianity, even as late as the 4th century ... still is not absolute, is not permanent. Yet, on the other hand, we can see even in
Paul's letters, which are the earliest literature we have from the early Christians, that the social separation in the communities he founded has already taken place. They're not meeting with the Jews. They're meeting in various households. So it's a varied change. It doesn't happen all at once and it doesn't happen in the same way, everywhere..."