Another piece of information that makes me believe Stanfa might not have been involved was the fact that he very easily could have been killed himself and had to be hospitalised for his injuries. Considering that Martorano was Bruno's regular driver, admitted his involvement in the murder and made a very clear effort to get out of driving Bruno home that night, it looks like, from Martorano's perspective, it wasn't safe to be the one driving Bruno (i.e., consideration may not be taken to keep whoever was driving out of it). It also seems reasonable that the visit to Stanfa in the hospital could have been to just figure out what was going on or, if Simone and Sindone were involved, to tell him not to worry because he wasn't the target of the hit. Could be involved, could also not be. George Anastasia can't even say for sure whether Stanfa was involved.

Gravano also gave a very in depth description of the Simone murder, the motive behind it and his meetings with Simone. He places the motivation squarely behind Simone's attempts to take over the family rather than as revenge for the Bruno murder. Now, of course, that doesn't mean the two motives are mutually exclusive. There would also be an ulterior motive to kill Sindone given his popularity and the fact that, as soon as he was dead, his lucrative rackets were taken over by his killers.

My point would be that considering Fresolone, Gravano and Friel point to other motives it's conceivable there's more at play here than a straightforward conspiracy involving all the players. Leonetti and Caramandi could very well be right that Sindone and Simone were involved, though when you have three other sources offering a different story, something else could be going on.

At the end of the day, we'll probably never know for sure as everyone identified as a suspect is now dead apart from Stanfa.