When Michael and Sollozzo change to speaking Italian over the restaurant scene, the subtitles don't pick up their dialogue. The conversation (translated in English) is in the novel. This goes back to the first novel. Puzo specifies that the Corleones make their money from illegal gambling and union corruption, which https://fellowfavorite.com/story19953694/the-greatest-guide-to-7-reason-why-the-godfather-master-piece