The Mafia doesn't want psychopaths. It needs people who are loyal, dependable, and trustworthy, and they test candidates rigorously to verify that they are "stand-up guys". But the Mafia recruits exclusively from the criminal population, so obviously a lot of psychopaths will slip past the screening process, more so than what you'd see in a legitimate corporation. The psychopaths who make it in are liable to get whacked because they are the ones skimming money, neglecting appointments, or disrespecting their colleagues.