He was obviously NOT happy with what hed found out about the FBI investigation.
I agree, and the only reason to get a Special Prosecutor would be to sort out the crimes committed and prosecute those responsible. Otherwise, Congress could do the investigation and issue a "report".
Well you raise a good point - a SP would at least be forced to file indictments. Congress might be far too inclined towards cover-up and whitewashing if they led the investigation. Perhaps Graham has dirty fingers, or maybe he was just duped. If he was duped into using allegations from the dossier in the debates - in other words, if he was tricked by Clinton backers who fed him fake oppo research to damage Trump - then he has reason to be angry and to want payback. (Or payola). Maybe he just sees the writing on the wall.