Mario Puzo freely admitted that he didn’t know all that much about the Mafia, and that much of what he wrote was based on hearsay, speculation, and Mafia anecdotes he’d heard second and third-hand.
Some of the characters are clearly based on real persons, others are composites. Among the characters who are OBVIOUSLY based on real persons:
Johnny Fontaine is obviously supposed to be Frank Sinatra. That Frank had close ties to major Mob bosses is undeniable. But the “Fontaine” subplot was based on a false, ugly rumor- namely, that the Mafia threatened Jack Warner’s life, in order to get Frank Sinatra the role of Maggio in the film version of “From Here to Eternity.”
Even Kitty Kelley, who trashed Sinatra in every way imaginable, acknowledges there was no truth to that story. In reality, Frak auditioned for the part, but lost the role to Eli Wallach. Shortly before filming was to begin, Wallach was offered a role in a Tennessee Williams play. SInce Maggio was only a small, supporting role, and Eli Wallach wasn’t a huge star, Warner Brothers let him go without a fight, and gave Sinatra (the runner-up) the part. Of course, that role reinvigorated Sinatra’s career.
Moe Greene was obviously supposed to be Bugsy Siegel, who squandered a lot of Mafia money while trying to build up resorts in Las Vegas.
Hyman Roth was obviously supposed to be Meyer Lansky.
As for composites… Don Corleone was partly based on Carlo Gambino. Like Corleone, Gambino was a (seemingly) sweet little old man who sat and sipped coffee, while munching on canoli, and smiling at little children. He ALSO hated drugs, and refused to make heroin trade a big part of Mafia business (though, in reality, loads of Mafiosis dealt drugs in spite of the old man’s disapproval). And DOn Corleone’s relationship with Michael resembled that of mobster Frank Costello and his sons. Costello kept his own sons out of the Mafia, and sent them to college.
Interestingly, Puzo’s books and movies SHAPED the Mafia as much as they described it. Puzo found it amusing that “godfather” became an important term in the real-life Mafia, because it was NEVER used by real mobsters in the 1940s. “Compadre” was something an ordinary Sicilian would call his buddy, NOT something anyone would have called a Mafia kingpin.
Over the years, many Mob guys came to LOVE the Godfather books and movies, which they thougfht glamorized their business!