As is usual for gangster bios, there's a lot of speculation about Tough Tony but not much hard evidence. The most logical answer to your question is that Tough Tony was a great earner through his waterfront rackets--you can never go wrong in Mobdom by following the money.

Lots of sites say Tough Tony, fearful that Genovese was going to whack him, talked to the FBI a year before his death in '63. There's no hard proof of that. Genovese arranged for his brother's murder and had Gambino installed in his place. If Gambino let Tough Tony live, why would Genovese want to whack him?