First, the early Church believed in a post-tribulation Rapture (the Man of Sin would be revealed before the Rapture, 2 Thess. 2:1-3). To this was added the false belief that the Antichrist had already arrived (they spiritualized the Bible to make the Pope and the Catholic Church into the Antichrist, and the many centuries of persecutions into the Tribulation). With the Antichrist already here, they reasoned, Christ could return at any moment.
Here again is their logic:
The Post-Tribulation Rapture Position
+ The Antichrist has been Revealed Already
The Imminent Return of Christ
But then something else changed. With the resurgence of literal interpretation, biblical scholars realized that the Antichrist was NOT the Pope. They correctly placed the coming of the Antichrist and the Tribulation back into the unknown future. And the Church was left with a choice.
The Church could re-establish the correct belief that Christ would come for them AFTER the Antichrist was revealed, but if they did so they would lose the wonderful (though historically incorrect) doctrine that Christ could come for them at any moment.
The imminent return of Christ was in jeopardy of being discarded, and with it a very powerful motive for holiness—the fear of being caught in the act.
How could the Church save imminency? Perhaps the Second Advent could be divided up into two stages? The first being the Rapture (which could still happen at any moment) and the second being the Revelation (which is still in the correct post-tribulation position).
Let’s digress for a moment!
During these same Dark Ages (c. AD 1585), as already mentioned, many Christians believed that the Pope/Catholic Church was the Antichrist. This would not do at all, so the Catholic Church had some of her Jesuits write on the subject of eschatology or future things.
This was part of the Counter Reformation.
(Stay tuned, folks, it's about to get really good!)