Everyone obliged by being conveniently out in the open, for their easy killings
There's a little thing in the novel, that just after the executions several opposing capos switched sides and joined the Corleones. I've assumed that this meant they had been turned beforehand, and possibly led their bosses to slaughter
I doubt the “opposing capos†would have been in the know of “their bosses slaughter beforehandâ€
I don't think anyone outside of Vito and Michael knew anything about the baptism murders, by design, even Tom was kept out of the loop
Nobody was let in on, what Vito and Michael were planning until their
need to know
after the traitor [Tessio] revealed himself
