Thousands of people, but only a small proportion of the entire population, will place their faith in Jesus Christ during the Tribulation ( Revelation 6:9-11; Revelation 7:4; Revelation 7:9-17; et al.). Some interpreters have concluded from these verses ( 2 Thessalonians 2:11-12) that no one who has heard the gospel and rejected it before the Rapture will be able to be saved during the Tribulation. This view rests on taking the antecedents of "them" and "they" as being "those who perish" ( 2 Thessalonians 2:10) and interpreting "those who perish" as those who heard but rejected the gospel before the Rapture. However it seems more likely that 2 Thessalonians 2:10 describes all unbelievers in the Tribulation, not just those who heard and rejected the gospel before the Rapture. Satan"s power, signs, wonders, and evil deception ( 2 Thessalonians 2:9-10) will impress all people living on the earth during the Tribulation. Paul could say that those people do not receive "the love of the truth so as to be saved" ( 2 Thessalonians 2:10) and they "did not believe the truth, but took pleasure in wickedness" ( 2 Thessalonians 2:12). He could do so since these phrases describe all unbelievers, not just those who hear the gospel and willfully rejected it before the Rapture (cf. John 3:19,Romans 1:24-32). [1][source]
"By "the lie [2]" is apparently meant the denial of the fundamental truth that God is God; it is the rejection of his self-revelation as Creator and Savior, righteous and merciful Judge of all, which leads to the worship due to him alone being offered to another, such as the "man of lawlessness."" [3][source]
"It is a solemn thought that when men begin by rejecting the good they inevitably end by forwarding evil." [4][source]
If Paul wanted to correct the Thessalonians" erroneous conclusion that they were in the day of the Lord, why did he not just tell them that the Rapture had not yet taken place? Evidently he did not do so because he wanted to reemphasize the order of events resulting in the culmination and destruction of lawlessness in the world. Lawlessness was their concern. [source][source][source]
Paul"s readers could, therefore, be confident that the day of the Lord had not yet begun. The tribulations they were experiencing were not those of the day of the Lord about which Paul had taught them while he was with them. Furthermore three prerequisite events had not yet taken place. These were the departure from the Word of God by many ( 2 Thessalonians 2:3), the removal of the restrainer at the Rapture ( 2 Thessalonians 2:7), and the revelation of the man of lawlessness, Antichrist ( 2 Thessalonians 2:3). This is the chronological order of these events. [5][source]