In 2 Thessalonians, and what is the nature of the son of perdition who is being withheld? Is it a flesh and blood man - this Man of Sin?
Many Christians believe, as you can tell from these comments, that the end of the Man of Lawlessness must come soon after he is revealed. But the scripture does not say that. The word used to describe his end is "then," which denotes a sequence in time and not a time length.
When the scripture claims the Man of Lawlessness will be revealed, Paul meant revealed to Christ's true followers. All New Testament scriptures were written to Christ's true followers, so the revealing would be to them. They would recognize it.
Paul gives enough information to identify him here:
"3Let no one deceive you in any way, for it [the end] will not come until the rebellion occurs and the man of lawlessness—the son of destruction—is revealed.
4He will oppose and exalt himself above every so-called god or object of worship. So he will seat himself in the temple of God, proclaiming himself to be God.
5Do you not remember that I told you these things while I was still with you?
6And you know what is now restraining him, so that he may be revealed at the proper time.
7For the mystery of lawlessness is already at work"
First notice that in vs6 Paul claims they knew what was restraining him, and that his lawlessness was already at work. So this could not be a single man as many Christians claim. Because no single man lives from the day of the apostles until Christ comes. Second, note Paul's scripture (vs4) does not say he sits himself down in the temple of a false god. It says he sits down in the temple of God. So he sits down inside the Christian congregation, since the congregation (it's individual members) is described as God's temple. The Man of Lawlessness' appearance is associated this with a rebellion. Where would this be? Obviously inside the church he sits down in. He (those that are part of this group)) raises himself above every so called god, and object of worship, thus demanding Christians follow him (them), making himself (by their teachings) a god to those who follow him. As Christ said, "worship your god and serve him only."
The type of lawlessness Paul spoke of was existent when he wrote this. However, it might not have been recognized by the average Christian, because something was retraining its obvious appearance. vs
7 "For the mystery of lawlessness is already at work. Only he who now restrains it will do so until he is out of the way.
8And then the lawless one will be revealed"
That should be enough to figure everything about it out. Paul was writing about apostasy inside the Christian congregation that would grow until it could be clearly seen by Christ's true followers. It would grow so large that it (the apostasy) would seat itself in a controlling position over many Christians. Paul was one of the chief Christians that restrained it from getting that kind of firm grip over the congregation while he lived. Thus he said in vs
6 "And you know what is now restraining him." Where Paul established congregations the members in those congregations knew Paul stopped false teachings from spreading inside them. The other apostles also served to retrain the apostasy. After the apostles died there was no single person, or single group inside the Christian congregation to restrain the false teachings from strong elders who eventually asserted themselves into a clergy class inside congregations. And in some churches, even in whole denominations, Christians are only acceptable members if they follow beliefs, right or wrong, of their clergy. Thus the clergy has established itself as a god, inside and over some members, who are the temple of God.
Read Paul's letters. Also read Peter, James, Jude, and John's Revelation that speaks of Babylon the Great, "a city that is over all the kings of the earth." You might also look into the history of the church which confirms Paul's words. It's historical actions reveal its apostasy, even if your understanding of biblical doctrine needs improving, for everyone can understand the NT does not approve of much of its historical actions.
But their end will be when Christ comes. Read Matthew chapter 7.