The world may never know.<quoted text>
One hypothesis that I remember hearing was that Paul was in fact an agent provocateur for Rome, that he worked to diffuse the Messianic furor that was causing such problems in Jerusalem by changing Jesus from an apocalyptic preacher to a pseudo man-god. Once he broke up the Jewish sect founded by Jesus, he left, mission accomplished.
He may have been like Harold Camping, milking gullible people dry and then disappearing with the cash when Jesus never came back.
God loves frauds, or so it seems.