Because he made himself the Son of God (hoti huion theou heauton epoiēsen). Here at last the Sanhedrin give the real ground for their hostility to Jesus, one of long standing for probably three years (Joh 5:18) and the one on which the Sanhedrin voted the condemnation of Jesus (Mar 14:61-64; Matt 27:23-66), but even now they do not mention their own decision to Pilate, for they had no legal right to vote Christ’s death before Pilate’s consent which they now have secured.