I think the reason is that in America most of the Greeks who migrated had money. Most Italians were extremely poor. The Greeks settled in other areas with better living conditions, the Italians were in slums. If Al Capone or Luciano's family had settled in another part of New York or America, they don't become gangsters, poor or not. I don't believe that there is a Russian Mafia as here either. The Italian-American Mafia that we follow came out of the early part of the 20th century, it was a phenomenon that died. The Greeks were mainstreamed into society quicker, as were the Irish years earlier.