Older people in my family who visited Italy in the 70s and 80s said that the language in Italy is much different than when my great grandfather was born there. There were all different dialects for different regions of the country. Then after WW2 most people learned proper Italian in school from textbooks. Even in the early days of Italian immigration to America, Napolitans spoke of version of the language, Sicilians another, and so on. So as the next generation learned English, that was the common language for them to communicate, regardless of where in Italy their family came from.