Cicci welched breaking Omertà and caused a fair degree of damage to Michael's standing, certainly dented his “legitimacy” and testified against him

In fairness, I reckon FBI would have told him Pentangeli had survived Michael's murder attempt and played them against each other However Omertà is Omertà

Tom visited Pentangeli under protection, in an Army barracks with the FBI guys, to successfully persuade him to slit his wrists
So wherever Cicci was they would have got him too same as Fabrizio, Rosatos all would have got whacked No doubt