I see no indication historically that the Gospel and Paul's teachings were directed at Jews. Possibly the first Christians were Jews (if there were any Christians before Paul and his group). However, Paul preached to the "Gentiles," that is, those Pagans known as "God-fearers" who supported Jewish synagogues financially and who practiced a form of monotheism, but did not observe the 613 rules of the Jews. Thus a new reform of Paganism, that retained elements of their story of the dying and rising Lord and his Lady resonated with the God-fearers. Also the words put on "Jesus'" lips castigating the rule-bound Pharisees also resonanted with those reluctant to adopt 613 rules. Likewise Paul's opposition to circumcision resonated. A popular reform. Still with us today. But it was not given to actual Jews, who would have known the Pagan story of Lord and Lady and automatically rejected it. I think probably there was a preacher known as Jesus of Nazareth and Paul built a story around him.