What explanation will the world give for the rapture's occurrence?  

The news media will likely be buzzing with all kinds of explanations for the mass disappearance of millions of people. Excuses may range anywhere from "aliens took them" to "these were the bad people and God removed them." The key factor is not the explanation but rather what has change at the rapture.

At the time of the rapture, God will limit back the working power of the Holy Spirit and people will be easily deceived by the devil and his followers. Satan will be given Satan a free hand to spread deception.

"And for this cause God shall send them strong delusion, that they should believe a lie" (2 Thess. 2:11).

There could be a period of profound regret and repentance following the rapture, but it will not come from the heart. Any contrite spirit will quickly fade as most people fall for the deception or shrink back from the realization that martyrdom may be the test of ones faith. However, there will be many who will see the truth and are willing to endure to the end.

"And ye shall be hated of all men for my name's sake: but he that endureth to the end shall be saved" (Mat 10:22).