HE was clearly from Sicily, and maybe he was some kind of free agent working in Staten Island and also in Sicily. He was close enough to Vito to be COnnie's Godfather, so that had to mean something. My best guess (the Oliver Stone posting aside) is that somehow he managed to do business in New York outside the direction of the five families, and possibly under the protection of Sicilians...perhaps Don Tomassino??? Vito would have given him the position of Connie's Godfather to assuage any hostility between him and his sponsors in Sicily and the Corleone families, and also to signal to the other families that he was aligned with the then powerful Corleones.