I think the verse is saying that God is going to do something to these people. The literal translation is that God is going to send them a "working of error", which to me means that they will no longer be thinking rightly. Their cognitive abilities will be sabotaged.
Since they would not receive the love for the truth, God will break their brains so they won't be able to know the truth. This will be during the time of the man of sin.
This is my understanding.
Much love!
