That's one of the reasons I think as I do on this. If we're talking about a departure from the faith, how is this a precursor? Since there has been apostasy from the faith all along. But there will only be ONE departure of the church.
Because it will involve a huge amount of Christians and they will be falling away to the false Christ, notably the last false Christ in a line of false christs. This last one will be the only one that will be able to perform miracles to deceive people into falling away to him.
Look at the context:
2Th 2:1 Now we beseech you, brethren, by
the coming of our Lord Jesus Christ, and by
our gathering together unto him,
Here the second coming is called "the coming of our Lord Jesus Christ and the rapture is called "our gathering together unto him".
2Th 2:2 That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us,
as that the day of Christ is at hand.
This day of Christ is directly linked to the two events of verse 1. Clearly the day of Christ is the day of the second coming and rapture. Paul wants people NOT to be troubled or confused about when these two events happen.
2Th 2:3 Let no man deceive you by any means: for that day shall not come, except there come
a falling away first, and that man of sin be revealed, the son of perdition;
Do not let anyone deceive you about when those two events happen! That day (second coming and rapture) will NOT take place until the Apostasy and the revealing of the man of sin take place and those are great tribulation related events. This proves that Paul placed the rapture after the events of the great tribulation and it's the second time Paul did this. He did the same here:
2Th 2:1 Now we beseech you, brethren, by
the coming of our Lord Jesus Christ (also known as the second coming) ,
and by our gathering together unto him, (reference to the Rapture)
There is a reference to the second coming and the Rapture! That's the subject!
2Th 2:2 That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that
the day of Christ is at hand.
A second
second coming reference!
2Th 2:3 Let no man deceive you by any means:
for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;
2Th 2:4 Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
That is the Antichrist! Claiming to be God causes the Apostasy or departing from the Christian faith and that takes place withing the great Tribulation. Paul teaches that the second coming and Rapture will NOT happen until the Apostasy and revealing of the man of sin happens plus he mentions that this man of sin will show himself as God and we know that happening during the great tribulation.
2Th 2:5 Remember ye not, that, when I was yet with you, I told you these things?
2Th 2:6 And now ye know what withholdeth that he might be revealed in his time.
2Th 2:7 For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.
2Th 2:8 And then shall
that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming:
The context is regarding the timing of the return of Christ and the rapture. That cannot happen until two important things occur.
1. The falling away/Apostasy
2. and the revealing of the Antichrist
Obviously it is the man of sin's appearance which causes the falling away because they fall away from Christ to him, the AC or false christ.
So it hasn't happened and isn't happening now. The AC must appear which will be a global event, then those who had followed Christ will follow the AC. Why? IMO he will claim to be Christ so they won't realize they have fallen away from Christ. This happened during the tribulation and as Christ states in Matthew, the second coming is not until the trib has ended.
Why did Paul even write this? Because people were concerned Jesus could just return at any moment without any warning (like a thief in the night) and Paul wanted to clarify that certain events had to happen first. Paul accidentally started the notion of the second coming happening at any time which is the basis for the pre-trib doctrine.
Contextually Paul was not speaking of a long period of falling away. It was a special event where people would stop being Christians and have a new God to worship and it is tied directly to the tribulation and the AC claiming to be God! Clearly it is when people are deceived and begin worshiping the AC because they think he is God. I believe many Christians will think he is Jesus Christ and won't realize they committed Apostasy.
2Th 2:3 Let no man deceive you by any means: for that day shall not come, except there come
a falling away first, and that man of sin be revealed, the son of perdition;
2Th 2:4 Who opposeth and exalteth himself above all that is called God, or that is worshipped;
so that he as God sitteth in the temple of God, shewing himself that he is God.
This has not yet happened but it is coming. Remember that the falling away is directly related to someone claiming to be God. They "fall away" to that false god.
Remember Christ's warning:
Mat 24:23 Then if any man shall say unto you, Lo, here is Christ, or there;
believe it not.
Mat 24:24 For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.
Mat 24:25 Behold, I have told you before.
Mat 24:26 Wherefore if they shall say unto you, Behold, he is in the desert; go not forth: behold, he is in the secret chambers;
believe it not.
There will come a time when people will believe Jesus has returned but it will be a false Christ.
1Ti 4:1 Now the Spirit speaketh expressly, that
in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils;
Here the Apostasy is said to happen in the "latter times" as opposed to over a long span of time. This places it at the great tribulation which also is a certain period of time just before the second coming.