The god of this age has blinded the minds of unbelievers so they cannot see the light of the gospel of the glory of Christ, who is the image of God. -2 Corinthians 4:4 BSB
The word “god” in this passage is about Satan.
The reason why the unbelievers are targets is that they have the potential of receiving Jesus Christ as their Lord and Savior. The devil and his demons will try to permanently keep them from believing in Christ by making their hearts harden so that no matter how much they hear the truth, they no longer have the opportunity to receive eternal life.
They are darkened in their understanding and alienated from the life of God because of the ignorance that is in them due to the hardness of their hearts. -Ephesians 4:18 BSB
Here is a verse that shows how it looks like when Satan accomplishes such deception in a person’s heart that even having Jesus in front of them, they still will deny the way of salvation that Jesus offers.
35 When Jesus heard that they had thrown him out, He found the man and said, “Do you believe in the Son of Man?” 36 “Who is He, Sir?” he replied. “Tell me so that I may believe in Him.” 37 “You have already seen Him,” Jesus answered. “He is the One speaking with you.” 38 “Lord, I believe,” he said. And he worshiped Jesus. 39 Then Jesus declared, “For judgment I have come into this world, so that the blind may see and those who see may become blind.” 40 Some of the Pharisees who were with Him heard this, and they asked Him, “Are we blind too?” 41 “If you were blind,” Jesus replied, “you would not be guilty of sin. But since you claim you can see, your guilt remains.” -John 9:35-41 BSB
The phrase “If you were blind,” Jesus replied, “you would not be guilty of sin” doesn’t suggest that being blind makes a person guiltless, but what it shows is that they haven’t come to the full knowledge of the gospel, which is the death, burial, and resurrection of the Lord Jesus Christ, allowing them the opportunity to accept the truth for their salvation. However, those who have come across the gospel of the Lord Jesus Christ and know the truth but still reject it are condemned to hell (see Hebrews 6:4-6). Some outright reject to follow Jesus, while others like the religious leaders of Jesus’ time, claim to follow God, but in actuality, they have rejected God by rejecting His plan through His Son. These are the ones who are called self-righteous by thinking that they see.