(2Th.2:1) Now we beseech you, brethren, touching the coming of our Lord Jesus Christ, and our gathering together unto him; (2) to the end that ye be not quickly shaken from your mind, nor yet be troubled, either by spirit, or by word, or by epistle as from us, as that the day of the Lord is just at hand; (3) let no man beguile you in any wise: for [it will not be,] except the falling away come first, and the man of sin be revealed, the son of perdition.
Here we see that we are not to be deceived and that the coming of the Lord for His church will not be except the "falling away come first and the man of sin be revealed". This falling away is the tares being gathered together to be burned. Like Judas, this corporate son of perdition sits in the temple of God's people, "setting himself forth as god" (verse 4) and deceives those who do not love the truth (verse 10) with his lying signs and wonders (verse 9), who will be destroyed at the coming of the Lord.
Many will be beguiled by this corporate false Christian (verse 3). Before the coming of the Lord, God is sending a delusion (verse 11) to cleanse His church of those who do not love truth. He is gathering the tares "in bundles to burn them" in the day of the Lord.
Starting in the middle of the tribulation, the mark of the beast will gather the tares in bundles to burn them. They will be "gathered out of His kingdom" but not yet out of the earth: that happens in the day of the Lord.
In 70 A.D., the true disciples had fled to the mountains (rapture) as Jesus commanded, but the apostates were "gathered" into the city to be destroyed by the Roman Beast. The church will be prepared to meet Him but the falling away must happen first.
First, God will "gather out of his kingdom all that cause stumbling and they that do iniquity and shall cast them into the furnace of fire" (the day of the Lord)."Then shall the righteous shine forth as the sun in the kingdom of their Father" (Matthew 13:41-43). First "he will sever the wicked from among the righteous" (verse 49); then He will come for His saints and destroy the wicked (2 Thessalonians 2:8).