John speaks of national unbelief in his gospel. Despite the many signs that Jesus does, they do not believe in Him as a nation. Their belief is irrational.
Such unbelief had been predicted by the prophet Isaiah. The clearest passage concerning the suffering of the Servant is Isaiah 53:1-12. Israel would not perceive God’s revelation concerning the Servant. Isaiah 53:1 implies that only a few have believed.
John quotes Isaiah 6:10 in order to explain that the nation as a whole was unable to believe. They consistently rejected God’s revelation of the Messiah. He had punished them with spiritual blindness and deadened hearts. They refused to believe. Note John 12:37 says “they would not believe.” Note the following verses:
Isaiah saw the Lord in a vision. Isaiah 6:3. John wrote that this glory Isaiah saw was Jesus’ glory. Jesus is Yahweh! See John 1:18; 10:30; 20:28; Col.2:9. Jesus in His nature is God (but God the Son is distinct in person from God the Father and God the Spirit). Isaiah spoke of Him. Many of Isaiah’s prophecies predicted the coming Messiah, Jesus of Nazareth. See the following verses:
Despite the massive national unbelief, the situation was not hopeless. God had a remnant in the Old Testament, and He has a remnant in the New Testament. There were believers in high places who believed in Jesus. Fear of being excommunicated caused them to be silenced. They feared men’s opinions. They loved the praise of men rather than God’s praise.