This is similar to verse 45:
45 But because I speak the truth, you do not believe Me.
Those who are in this world have been blinded so that they cannot see the truth, even when it is right in front of them:
2 Cor. 4:3-43 And even if our gospel is veiled, it is veiled to those who are perishing, 4 in whose case the god of this world has blinded the minds of the unbelieving so that they might not see the light of the gospel of the glory of Christ, who is the image of God.
This is why it is important to pray for them, that God would reveal Himself to them.
Eph. 6:1212 For our struggle is not against flesh and blood, but against the rulers, against the powers, against the world forces of this darkness, against the spiritual forces of wickedness in the heavenly places.