I watched the original hearing, then re-watched it.   McCain is an ex-officio member of the committee along with Mitch McConnell. (Title is window dressing). He rarely, if ever, appears at committee hearings. His apparent incoherence was embarrassing and attributed to, as you suggested, to fatigue and medication.  Unlike you, however, I don't trust him.  His military record is to be commended, but his political record  is dubious.  He was knee-deep with Charles Keating.  (The story of every politician).