Edit: fixed an error I made during copy paste
Went to check context…but boy, do you need a lot of context to get what this in reference to. Spoiler: the stand-alone quote isn’t far from the in-context meaning:
Thessalonians 2:
1 Concerning the coming of our Lord Jesus Christ and our being gathered to him, we ask you, brothers and sisters, 2 not to become easily unsettled or alarmed by the teaching allegedly from us—whether by a prophecy or by word of mouth or by letter—asserting that the day of the Lord has already come. 3 Don’t let anyone deceive you in any way, for that day will not come until the rebellion occurs and the man of lawlessness is revealed, the man doomed to destruction. 4 He will oppose and will exalt himself over everything that is called God or is worshiped, so that he sets himself up in God’s temple, proclaiming himself to be God.
5 Don’t you remember that when I was with you I used to tell you these things? 6 And now you know what is holding him back, so that he may be revealed at the proper time. 7 For the secret power of lawlessness is already at work; but the one who now holds it back will continue to do so till he is taken out of the way. 8 And then the lawless one will be revealed, whom the Lord Jesus will overthrow with the breath of his mouth and destroy by the splendor of his coming. 9 The coming of the lawless one will be in accordance with how Satan works. He will use all sorts of displays of power through signs and wonders that serve the lie, 10 and all the ways that wickedness deceives those who are perishing. They perish because they refused to love the truth and so be saved. 11 For this reason God sends them a powerful delusion so that they will believe the lie 12 and so that all will be condemned who have not believed the truth but have delighted in wickedness.
Thought I had it too, but after starting to type it out realized there was a flaw in my logic.
So basically my understanding of this after some more reading:
People are thinking that the rapture happened, so one of Jesus’ people are telling them it hasn’t since there needs to be a powerful anarchist and/or Anti-Christ that comes about (the “lawless man”). The anarchist is gonna have powerful magic and will be preaching that he’ll give the people a better life than god or whatever to get them off the path of god.
Okay cool, so the people (who are pre-sorted by god into the godly and condemned) will see this guy and some will be tempted by the lawless man, but won’t necessarily do anything to deviate from.gods path. So god is gonna come along and do something* to make them actually deviate from the path of god (which is the delusion).
*the specific Greek phrase used in the original text is only used once here and so there isn’t a good bead on what that delusion is/could be. The key thing appears to be that god will actively do something to make the damned be damned.