But though He had performed so many signs before them, yet they were not believing in Him.
While the purpose of Jesus' miracles was the authentication of himself and his word (Hebrews 2:1–4), that fact should not lead us to believe that miracles have any power to convince unregenerate minds (Luke 16:31). Calvin writes,
That no man may be disturbed or perplexed at seeing that Christ was despised by the Jews, the Evangelist removes this offense, by showing that he was supported by clear and undoubted testimonies, which proved that credit was due to him and to his doctrine; but that the blind did not behold the glory and power of God, which were openly displayed in his miracles. First, therefore, we ought to believe that it was not owing to Christ that the Jews did not place confidence in him, because by many miracles he abundantly testified who he was, and that it was therefore unjust and highly unreasonable that their unbelief should diminish his authority. But as this very circumstance might lead many persons to anxious and perplexing inquiry how the Jews came to be so stupid, that the power of God, though visible, produced no effect upon them, John proceeds further, and shows that faith does not proceed from the ordinary faculties of men, but is an uncommon and extraordinary gift of God, and that this was anciently predicted concerning Christ, that very few would believe the Gospel.
—John Calvin, Calvin’s Commentaries Volume XVIII (Baker Books, 2009), Commentary on the Gospel according to John, 2:40.
Only one miracle has the power to produce faith, and that is the miracle of regeneration (John 3:4–8).