To me the power breaks down like this;
Rastelli is boss, but ineffectual, he's only as strong as the capos on the street loyal to him..
The capos on the street loyal to him, their strength is that when they go see Rastelli and come back to Brooklyn, they can say " Rusty wants this", so they are the word of the boss, but they are not the big earners, but plenty tough..
Galante had more prestige than Rastelli, being Bonnaos underboss, similar to Genovese when he was a capo with like Boss level power. He had the control of the dope, so he was a powerhouse earner, and had Sicilian muscle. But he was isolated from the rest of the Bonnano family, and the Commision..
Now Sonny Black has like four, five crews following him, so he had the military might, and the most say on the streets I'm guessing, Also had the Chin, so with the Commision he was solid. Was a great earner and had earners with him, that was the problem I think, like he was already rich and he tried to stiff the Sicilians.
Plus he wasn't too cool with the Massino Group, so he was isolated as well, but in order neutralize him they had to hit all those guys at once...