Because family is at the heart of the Mafia
There are three first cousins from Corleone who immigrated to New York around the same time, and had the same name: Stefano la Sala. One would become known as Steve LaSalle, a high-ranking member of the Lucchese crime family for half a century.
When the Fascists rose to power in 1922, it soon declared a war on the mafia in Sicily, nearly wiping them out, and forcing di Carlo to flee. Meanwhile, his future associate, a Fascist propagandist, was making a name for himself in the United States.
The rise of fascism in Italy nearly destroyed the Sicilian Mafia before the end of WWII, but due to the political blunders of the Allies following Operation Husky, the Mafia was able to reform itself under their protection. Angelo di Carlo, a veteran of the Italo-Turkish War in Libya, is considered one of the architects of this renaissance.
Mafia Genealogy 