I completely agree, Ricca & Accardo were the two most elusive, long-term successful Outfit figureheads of them all. Their combined respective time spent outside of the joint is a mind-blowing stat.

For Ricca, it was pure cunning & absolute power/ruthlessness. He was truly the great one.

For Accardo, it was a combination of luck, savvy, & hiding behind other guys. Accardo was never as powerful as other top guys, he didn't have the rackets, wasn't a gambling guy, etc. He knew a lot about politics, knew how to butter up to top politicians, that is why Accardo was useful to the Chicago Outfit. He never made top decisions, never had the final say in anything. He was an intelligent guy, no doubt, and he was always loyal & friendly with other gangsters, which is why no one ever had the desire/reason to toss him under the boss.