I have never heard this before. It seems very plausible that Maranzano knew Angelo Caruso wasn't the type to have ulterior motives. He just didn't have the ambition of other Mafioso but that decision cost him his life. The Young Turks knew Angelo Caruso and for that matter some other members wouldn't kick up a fuss. Most of the crews by then just wanted to the war to be over. With Bonanno coming into power with his family lineage and the blessing of Lucky Luciano, no one was gonna retaliate. But there was some opposition to Bonanno's ascension and the murder of Maranzano. Francesco Italiano and Fillipo Rappa were the main rivals of Bonanno. Whether or not they actually had enough power be strong then Joe himself is another story.