Christianity was based on Jesus, who claimed that his purpose on Earth was to reform his Jewish religion, which had become corrupted by Greek and Roman conquest and influences. At least that is what he said. But he was condemned for violating the commandments of traditional Judaism.
The actual Christian religion is more the work of Paul of Tarsus. Jesus did not intend to create a world religion, he wanted to restore Judaism. Paul saw that Jews were fractious and much fewer in number, so he dedicated his life to converting pagans.