The high priest just did not believe that Jesus the Son of God was actually human. He as well as others, apparently expected God "supernaturality" to show on his face. They did not see or hear that he descended from heaven and had a radiant light shining around him, hence, He could not be the Son of God.  Also, the fact that Jesus was "lowly and humble" sanctioned their belief. From the question, "can anything good come out of Egypt?" it is evident that the high priest answered the question negatively!