His religion was certainly less aggressive and abrasive than the teachings of John, so I can't see why the religion would become popular outside of peasantry in the easternmost parts of the Roman Empire
IIRC there were numerous arabianized christian sects that attempted to unite arabia in the 600s
maybe they christianize the fertile crescent through osmosis and trade? zoroastrianism was already on the way out during the 600s-700s anyway.