While I believe that Joey Gallo was involved, I feel that Gambino was the main factor in this and the two of them had some type of agreement. I'm pretty sure that all the bosses wanted Colombo gone by that point and approved it, but keep in mind the other families had relatively weak bosses at the time. Genovese boss Tommy Eboli would be taken out the same year as Gallo, Tony Ducks was just getting out of the can and solidifying control of his family, and the Bonannos had been in shambles since Joe Bonanno was forced into retirement. Long story short, Carlo WAS the commission so he pretty much did whatever he wanted.