Iscariot wasn't a last name. Iscariot was a location. He was Judas of Iscariot. Iscariot was a town in the southern Judea / northern Edom region. Judas was likely an Edomite.
"Herod was an Idumean." - Josephus, Antiquities of the Jews
The Edomites were mongrels intermarried with Canaanites and enemies of Israel and Judah (two seperate kingdoms).
The pharasees were likely Edomites also. Herod had absolute power and would have replaced all the Judean high officials with relatives and like-minded individuals. THAT is who killed Christ. Edomite/Canaanite converts to Talmudic Judaism.