Their unbelieving minds are so blinded by the god of this passing age, that the gospel of the glory of Christ, who is the very image of God, cannot dawn upon them and bring them light.
Nothing is pure to the tainted minds of disbelievers, tainted alike in reason and conscience.
They profess to acknowledge God, but deny him by their actions. Their detestable obstinacy disqualifies them for any good work. Therefore God puts them under a delusion, which works upon them to believe the lie, so that they may all be brought to judgement, all who do not believe the truth but make sinfulness their deliberate choice. The place of utter destruction and ruin.