@Njein
Caruso represents the group that wasn't Castellamarese in the administration (similar to Angelo Bruno(sicilian) having Tony Caponigro(calabrian) as no #3 representing the Calabrian faction in Philadelphia). Bonanno was apart of a younger group (Himself, Gaspar Digregorio, Buster Domimgo, Natale Evola, Vincent Danna etc) who were bodyguard/hit squad for Salvatore Maranzano. Bonanno may offically been a capo but was closer to Maranzano because of his status as a bloodline Mafioso cousin to Boss Stefano Maggadino. I don't think at this time Bonanno was in command over the entire Family. I think once the war was over, Angelo Caruso had no desire to be the head of the Family (and he would have others oppurtunities in the future).Bonanno had a powerful lineage to their homeland Castellamare Del Golfo, He was proven tough in battle, alreasy had legitimate business interests and (IMO) was Recognized by The heavyweights (Luciano) as the person that needed to be dealt with in that group of people. Evenone within that family subsided except Frank Italiano and the family didn't back him.

@mchang93
Alot of us give credit to Carlo Gambino but Luciano has a strong case as being Greatest Boss, in spite of all his misshaps(for me, long jail terms is usually a negative mark) but Lucky was so brillant and powerful, it almost negates it.