Infelice was part of a deeper crew, it took longer to climb the ranks & there were way more heavies in his crew. Just because Lumbo was made boss before Rocky doesn't mean much, you follow the rank of your crew. Cicero was an absurdly deep crew & Rocky had to wait in line.

Hell, Lumbo & the Mooch are on tape talking about avoiding on stepping on Ferriola's toes & steering clear of his territory.

Also, at the end, Rocky was arguably #1 in the entire org, Lumbo never was close to that.