‘Though he had done so many signs before them still they did not believe in him. This was in order that the word spoken by the prophet Isaiah might be fulfilled, “Lord, who has believed our report, and to whom has the arm of the Lord been revealed?” (Isaiah 53:1 LXX)'
John stresses here the people's blindness. They had heard Jesus' words, they had seen remarkable signs, and yet they refused to respond and believe. But He was not surprised for so the Scripture warned. The wondrous Servant of God spoken of in Isaiah 53 had come, but like the men of old they had failed to discern the hand of God in it. (Of course there had been those who had responded (John 12:11) but here the stress is on the majority who continued to be blind). Indeed John sees in this a vindication of Scripture. It was ‘in order that the Scripture might be fulfilled'. There was a divine necessity in it. Afterwards ‘they could not believe' (v. 39). God was not taken by surprise for He had warned of the situation beforehand.
This is the second time that a decisive rejection of Jesus is spoken of. The first was when many of His disciples would no longer walk with Him (John 6:66), even though He is 'the way' (John 14:6). This one tells us that many in the crowds would not believe in Him, even though He is 'the truth.' The third will come in John 19:15 when, even though He is 'the life,' the Jewish leaders will arrange for Him to be crucified and will rather choose Caesar.