“Tell us, when shall these things be? and what shall be the sign of thy coming, and of the end of the world?” (Mt. 24:3b)
From my book The Christian Church in the Last Days
The rapture would not generate the great falling away of 2 Thessalonians 2:2-3. The three components that Paul lists here…the rapture, the falling away, and the revealing of the son of perdition, must occur in the sequential order he gives. The question the Thessalonians are asking: “Did the rapture already occur and did we miss it?” is answered by Paul by saying that the rapture cannot happen until the falling away and the revelation of the son of perdition have occurred.
That this end-times prophetic question by the Thessalonians involves the rapture and not the second coming, is inferred by Paul and by the Thessalonian leaders writing to Paul, by the simple fact that both Paul and the Thessalonians are unquestionably saved but physically still on the earth and discussing this issue.
If the topic under discussion involved the second coming, the entire first-century church at that time understood correctly that Jesus Christ instead would then be openly ruling and reigning on earth, and the original question sent by letter to Paul would have been moot and nonsensical. Like today, the timing of the rapture within the sequence of end-times events was an unsettled question, and Paul gives additional information to the Thessalonians to the limits and extent of his inspired understanding.
Again, the people who would be “left behind” in a pretribulation rapture are left behind in place. “Left behind” is not synonymous with “falling away.” There is no remarkable movement of the “falling away” group if the main body itself…the raptured church…is the entity that has done the actual moving away through a physical disappearance. The world-at-large would not therefore view the non-raptured churchgoers, who would stop attending a non-existing church because it was now pointless to do so, as the New Testament prophesied “great falling away.”
If the true church of believers is lifted off the earth in large numbers pretribulation, who in the world would take much notice of, or care about leftover churchgoers “falling away” as the result of merely being left behind like everyone else following such a cataclysmic event as the rapture? Such a falling away, after-the-fact of the rapture, would be anticlimactic, comparatively inconsequential, and barely worth noticing. It would have trouble getting news-media coverage on the back page of the newspaper, because a post-rapture falling away would be a non-event.
To constitute a noticeable falling away capturing the attention of the world, worthy of mention in biblical end-times prophetic scripture, the Christian church must still be fully in attendance on earth. This includes all of the saints of God who will eventually be martyred or raptured, and includes all of the nominal, unsaved churchgoers who will “fall away” as a result of an as-yet-to-be-determined, currently unknown reason.