I don't think Gallo was involved, I think it would have been run by the commision, and I doubt they would have given a loose cannon like Gallo the go. If Gallo and his crew were involved I think his brother would have been killed also, or shelved in the very least. I figure the other bosses decided Colombo was bringing too much heat with the Italian American Civil Rights League, and got together with other high ranking members of the Colombo family and devised a plan.