What does Pistone have to do with the downfall of the Lucchesse's he was undercover in the Bonanno family. If your saying Pistones part in the comission case had to do with it I don't think he was all that important in the evidence for the commission case I mean yeah his work was part of it but there was a lot more important evidence in that case then what came from Pistone.
I'm just coming off of reading Donnie Brasco: Unfinished Business.
Basically Pistone claims that his 6 year deep cover operation ensnared mobsters from multiple families, including the Luccheses. He actually met with Tony Ducks Corallo and testified that Ducks was the Lucchese boss. Remember that RICO is about conspiracies which is collaboration. Different families collaborated together. Basically Pistone met with Ducks as a Bonanno associate, and then helped put Ducks away by itestifying, thus lopping off the Lucchese leadership. In that leadership void, the Lucchese's fell into chaos.