If that was the case, Massino wouldn't of tried to keep Sciascia's murder a secret from him, in fear of some sort of retaliation.
I don't think it really had to do with Vito. Even as a boss, killing one of your most important capos over nothing without informing the other families first, or even your own capos, can destabilize your position as a boss.
"It was between the brothers Kay -- I had nothing to do with it."
