I agree he disobeyed his boss and ratted on his boss. Don Carlo was a master strategist used it to gain control of another family be keeping Colombo as boss. From what I've heard Don Carlo had been trying for years by supporting Gallos and Colombo just brought it to his door step. Profaci family members of that time woulda took anyone as boss who wasn't Profaci or an extension of his rule. Profaci and his UB when he took over were bleeding their family dry and all money went all the way to top.