Finally, in the itw, he said Phil Testa made Pete Casella Underboss and not Scarfo because Casella was Sicilian like Testa (Scarfo being Calabrian). I don't think that was the reason. My guess is that Testa knew Scarfo had a lot of power and was close to NY so makin him the Nr.2 would have threatened his leadership. We all know what happen then.
I disagree for a couple of reasons.
I think if Testa seriously considered Scarfo a threat rather than an ally we would know about it already through Leonetti (either in his book, interviews or in the information he provided to reports from the NJ SCI). We haven't seen any information to lead us to believe that Testa and Scarfo's relationship was strained at this point and in fact, the evidence we do have points to the contrary.
I.e., Scarfo pushing for Testa to become boss in the mid-late 1970s; Testa wanting Scarfo to replace Joe Rugnetta as consigliere; Scarfo siding with Testa in his dispute with Bruno; Scarfo promoting Testa to take over following Bruno's murder; their joint involvement in killing threats to their new leadership (John Simone, Frank Sindone).
Regarding the Sicilian and Calabrian factions, Leonetti's claim is supported. From 1959 to 1981 you have an uninterrupted pattern when it comes to the top administration positions. Angelo Bruno and Phil Testa were Sicilians and they chose fellow Sicilians as their underbosses (Ignazio Denaro and Testa for Bruno; Casella for Testa). The consigliere on the other hand was always Calabrian (Rugnetta, Caponigro, Scarfo). In the case of the Philadelphia family, the position of consigliere in the 1960s and 1970s was viewed as not simply the number three man in the hierarchy but as the head of the Calabrian faction. When Joe Rugnetta died in 1977, the only serious* contenders to replace him were all Calabrians (Testa wanted Scarfo, others speculated that Nicholas Piccolo would get it and, finally, the Calabrian faction chose Caponigro for the position). One could make the argument that, while the consigliere is often generalised as the number three role in the family, the consigliere can hold more influence than the underboss at any time (e.g., Philip Rastelli considered Stefano Cannone, his consigliere, as his number two). The general consensus appears to be that Scarfo, as consigliere, carried more weight in the family than Casella did as underboss.
Casella also didn't come out of nowhere. His appointment was a surprise and, ultimately, a very bad decision but it wasn't without reason. Casella was a long-time member who had done considerable prison time for the family and he had also set up a couple of meetings for Testa in New York after Bruno was killed.
*while not seriously considered for the role, the Sicilian Antonio Pollina made it known he wanted to be consigliere after Rugnetta and was politely turned down by Bruno
