The rapture doctrine is what Paul was referring to with his notice of the delusion. The apostasy or falling away is easy to grasp. It means what it means. There will be a falling away, but not as many understand it. The falling away can, and rightly so, be interpreted as those who cling to this delusion as those who find the truth move forward, while the deluded stay behind. As they move forward those that resist the truth can been seen as falling away or behind.
When the false Christ rises those who rely on the Rapture doctrine will not recognize him for who he really is, because they believe the man of sin cannot appear while they are still here. That is the meaning of the warning that he will deceive many. Paul wasn't talking to the the heathen, he was saying that for our benefit.. He will re-interpret the scriptures and will posture himself as the long awaited coming Messiah,
There is much I can say on this topic
When the false Christ rises those who rely on the Rapture doctrine will not recognize him for who he really is, because they believe the man of sin cannot appear while they are still here. That is the meaning of the warning that he will deceive many. Paul wasn't talking to the the heathen, he was saying that for our benefit.. He will re-interpret the scriptures and will posture himself as the long awaited coming Messiah,
There is much I can say on this topic