First and Second Thessalonians should never be studied separately. Second Thessalonians is a response to the Thessalonian’s response to First Thessalonians. Both are about the Resurrection. The resurrection of the dead is key.
2 Thess. 2
2 Now we request you, brethren, with regard to the coming of our Lord Jesus Christ and our gathering together to Him, 2 that you not be quickly shaken from your composure or be disturbed either by a spirit or a message or a letter as if from us, to the effect that the day of the Lord has come.
3 Let no one in any way deceive you, for it will not come unless the apostasy comes first, and the man of lawlessness is revealed, the son of destruction, 4 who opposes and exalts himself above every so-called god or object of worship, so that he takes his seat in the temple of God, displaying himself as being God.
5 Do you not remember that while I was still with you, I was telling you these things?
***3 Let no one in any way deceive you, for it will not come unless the apostasy comes first, and the man of lawlessness is revealed, the son of destruction, 4 who opposes and exalts himself above every so-called god or object of worship, so that he takes his seat in the temple of God, displaying himself as being God.
5 Do you not remember that while I was still with you, I was telling you these things?***
It doesn’t get any clearer than that. Which is why no one else responded to it. You can’t cherry pick a verse here or there. Context means everything.