Paul had taught them then reinforced to them that Believers would not be going through the Tribulation to come (1 Thess 1:10). Had he not taught them such they would not have been upset by the fraudulent letter.
If they had been taught to expect going through at least part of the Tribulation the letter would not have frightened them since the trials they were enduring would be a sign of the imminent return for them.
The hour / time of testing of the unbelievers / earthdwellers is what Jesus assured the churches He would keep them from. The beginning of the seals broken began the testing as shown starting in Rev 6. Notice that the Rev Chaptr 3 is a message not to just the Philadelphis church but to the churches, plural:
Rev 3:13 “He who has an ear, let him hear what the Spirit says to the churches.”
And what had the Spirit just dictated in the Philadelphia Letter? ...
Rev 3: 10 Because you have kept My command to persevere, I also will keep you from the hour of trial which shall come upon the whole world, to test those who dwell on the earth.
we agree it is Jesus opening the seven sealed scroll, in Heaven, with the redeemed witnessing it, in heaven. That first seal releases the antichrist upon human kind. For satan's man to be released upon humankind the one restraining him prior to that release is taken out of the way. The Holy Spirit indwelling the born again spirits of the Body of Christ no longer restrains the release/
2 Thess 2:1 Now, brethren, concerning the coming of our Lord Jesus Christ and our gathering together to Him, we ask you, 2 not to be soon shaken in mind or troubled, either by spirit or by word or by letter, as if from us, as though the day of Christ had come. 3 Let no one deceive you by any means; for that Day will not come unless the departure comes first, and the man of sin is revealed, the son of perdition,
That message to the questioning Thessalonians indicate to me that the Day of the Lord cannot come UNTIL the restraining force is removed from restraining the man of satan's choosing. If the man of sin cannot be revealed until the departure happens then the treaty with Israel will not happen until the restrainer is removed ... to allow the antichrist to ride upon the scene.
“...that Day will not come unless the departure comes first,...”
What version renders it “departure”?
Even Darby’s own renders it “apostasy.”
Others use “rebellion,” “revolt,” “falling away,” “turning away” — the only sense in which “departure” can possibly be rightly applied is that of “departure from the faith.” Your attempt to jimmy it in there as a reference to the rapture is no less than a barefaced misrepresentation of the true meaning of the text. Scores of translations and versions of the bible exist; I’ve scanned many, and nowhere have I seen “departure” used in this verse, and certainly not in the sense YOU want to convey: that of leaving a place.
You are certainly entitled to your interpretation of how the last times events play out. You are decidedly NOT entitled to rewrite scripture to support your interpretation.
“Paul had taught them then reinforced to them that Believers would not be going through the Tribulation to come (1 Thess 1:10).”
You here use “Tribulation” where most versions use “wrath.” Again,I ask what version you are using, because they AREN’T synonymous terms.
The Church is certainly spared from the wrath that is to come, but the jury is out on being gone before Tribulation breaks out. You say yes, I say no, and this is a big conversation in The Church.