According to Maccoby,
the founding of Christianity as a religion separate from Judaism was entirely the work of Paul of Tarsus.
Maccoby claimed that Paul was a Hellenized Jewish convert or perhaps even a Gentile, coming from a background exposed to the influence of Gnosticism and the pagan mystery religions such as the Attis cult, a myth involving a life-death-rebirth deity. The mystery religions, according to Maccoby, were the dominant religious forms in the Hellenistic world of that age and so, would have strongly influenced Paul’s mythological psychology. Maccoby partially derived this theory from fragments of the writings of opponents of Ebionites, particularly in the treatise on Heresies by Epiphanius of Salamis.
Maccoby considered Paul’s claims to an orthodox Pharisaic Jewish education to be false, asserting that while many of Paul’s writings sound authentic to the uninitiated, they actually betray an ignorance of the original Hebrew scripture and the subtleties of Jewish Law[2]. Maccoby claimed that an examination of the New Testament indicates that Paul knew no Hebrew at all, and relied entirely on Greek texts that no actual Pharisee would ever use because they were not properly translated.
According to Maccoby, Paul fused the historical story of Jesus’ crucifixion with elements of contemporary mystery religions and Gnosticism, developing such new non-Judaic mythic ideas as the Trinity and the Last Supper. Paul also made an attempt to find prophetic justification for his newly created myth in the Old Testament. Paul came to present Jesus as a dying and rising savior deity similar to those from the Hellenistic mystery cults, fused with the historical pedigree of Judaism, thus giving birth to a powerful new myth whose preaching gained him a large following. As the Jerusalem group of the original disciples of Jesus gradually became aware of Paul’s teachings, bitter hostility ensued between them.
en.wikipedia.org/wiki/Hyam_Maccoby