2 Thess 2 Pre trib

Paul is beseeching the Thessalonians by the rapture “by the coming of our Lord Jesus Christ, and by our gathering together unto him” v1. Followed by him stating that “the day of Christ” is not at hand but is after the falling away and the man of sin being revealed. Post trib conflates ‘that day’ with our gathering unto him. Peculiarly they never seem interested in why the church would be “soon shaken in mind, or be troubled” at the prospect of Jesus’ return being at hand... really! One would think the biblical response to Jesus saying “Surely I come quickly” would be “Amen. Even so, come, Lord Jesus.” (Rev.22:20) If Jesus coming and our gathering unto him was at hand we would ‘rejoice with exceeding great joy’. This is what Paul told the Christians after revealing the rapture in 1 Thess.4 to this same church; that “ye sorrow not” and “Wherefore comfort one another with these words”. (v13,18) Jesus told the disciples to not let their hearts be troubled and proceeded to tell them of his coming again to receive them unto himself and the place prepared in the Father’s house in heaven. (Jn.14:1-3) Had they been taught by Paul a post-trib rapture, they would not be troubled or terrified that they were in the tribulation prior to Christ's return (Mt.24:6, Mk.13:7, Lk.21:9). Rather they would know to "then look up, and lift up your heads; for your redemption draweth nigh." (Lk.21:28) The coming of Christ would comfort them in that case. Furthermore the post-trib position would have Paul here comforting Christians with the coming of the man of sin, great tribulation, fearful sights and that the Lord delayeth his coming!

This however, is why he was beseeching them in v1 by the rapture of the church so as to comfort them. They were confused (by spirit or word or letter) that they had been cast into great tribulation and were shaken in mind and troubled. In contrast to our gathering unto him, when Paul mentions “that day” or “the day of Christ” he is referring to “that day” in 1:10. This is the 24 hour day at the return of Christ to the earth, preceded closely with events causing men's hearts to fail. (Mal.3:2, 4:5, Joel 2:31, Amos 5:18,20, Isa.13:6, 9, 13) He comes in flaming fire taking vengeance with his mighty angels to punish with everlasting destruction (v7-9) when “he shall come to be glorified in his saints, and to be admired in all them that believe... in that day”.
Some translations have v2 as 'day of Christ had come'. If the Thessalonians believed post trib this make even less sense. For then the saints would be troubled that Jesus had already come and returned to the earth to reign. How would they have thought they didn't notice the great tribulation described in Mt.24 and the return of Christ in judgment to the earth? And why would they be troubled at the idea that Jesus had already returned and was on the earth?

If the Thessalonians had been taught pre-trib it makes perfect sense as to why they were troubled that the coming of Christ in wrath was imminent (at hand- KJV) and that the rapture of the church had already happened. And why he was comforting them with rapture in v1. And telling them why the return of Christ to the earth wouldn't happen before certain signs.

This video and description info should also help- The Millennial Day is at Hand
• The Millennial Day is at Hand