chapotraphouse

Many, not all. Paul’s letters established the practice of converting to Christianity directly from polytheism without assuming Jewish practices first.

That said, on the eve of Christianity, Many Romans casually adopted parts of Jewish belief and practice, sort of like celebrities in the 2000s doing Kabbalah. So the line of who was and wasn’t Jewish was kinda blurry. At least before the council of Nicea and Constantine, most Christians were probably considered Jews by the Romans, and Heretics by the nascent Rabbinic movement.

Paul converted Gentiles, the Johannine school was likely mixed, and the First Council of Jerusalem was largely about the independence of Paul and the lack of a need for Gentiles to follow Jewish Law. By 150 the vast majority of Christians were non-Jewish in ancestry. Many of the 1st/2nd century Church Fathers, like Irenaeus, Clement I, and likely others were non-Jewish. You also had non-Jews worshipping the Abrahamic god for at least the 1st century BCE

You can generally break down the early branches of Christianity into three cross pollinating branches

Jewish Christians - Lead by the moderate Peter and the more strictly Jewish James. Largely died out or was subsumed by other branches.

Pauline Gentile Christians - What became the main branch of Christianity in organisation.

Mystic Christianity - This includes both the Proto-Gnostics and the Johannines. Highly mixed in with other mystic/apocalyptic Jewish and Middle Platonic sects, and largely comprised of fairly educated Hellenistic Jews and Gentiles.

Their relative education and theological hot-housing meant that the Johannine school ended up cross-pollinating with the Pauline school and almost co-opting their theology (the Johannine Irenaus and composite theology of Justin Martyr shooting down the "hyper-pauline" heresies of Valentius and Marcion.)