I would have to agree that Paul was the logical choice for the Family's future, as Gambino knew that the times were changing,and sophisticated semi-legit rackets were the new business opportunities. There would still be a need for leg breaking,psychotic sadists in the Family,just not in the top spot. Also Paul was both brother-in-law and first cousin to Gambino (what a world). Lastly ,there is some speculation that Neil was passed over because of his prior involvement with a made guy's wife,and that Gambino never forgot it.