Hiram is a reflection if the time, and a reflection even of now. The New York mafia often had, and still has, Jewish associates. No one who who doesn’t have the correct heritage, in this case, Italian, and in the 1930’s, more specifically Sicilian*, can become made-men. But the mafia does have a long history of working with Jewish associates. And it makes sense. These are two Caucasian groups who, along with Irish, faced steep discrimination, and still face it in the case of Jewish people. I’m not going to sanitize history when I write historically-set pieces.
*Over time, heritage requirements have changed, from full Sicilian, to just full Italian, to half Italian on your father’s side, and back to full. In the 1930’s, both the New York and Chicago mafias required that members be fully Sicilian.