7 And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels,
8 And prevailed not; neither was their place found any more in heaven.
9 And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
(Rev 12:7-9 KJV)
After God casts these angels out, they land on earth pretending to be ufo aliens, claiming they seeded the Cambrian strata with life...and mankind with belief in God and the human soul...
The falling away is the entire earth believing the lie, it comes first so that the Antichrist can rise, and he won't be representing former religions, such as Christianity, he is the Christ of a new god, a god of forces, a new god unknown to mankind, and he will claim its power makes him God:
3 Let no one deceive you by any means; for that Day will not come unless the falling away comes first, and the man of sin is revealed, the son of perdition,
4 who opposes and exalts himself above all that is called God or that is worshiped, so that he sits as God in the temple of God, showing himself that he is God. (2Th 2:3-4 NKJ)
36 And the king shall do according to his will; and he shall exalt himself, and magnify himself above every god, and shall speak marvellous things against the God of gods, and shall prosper till the indignation be accomplished: for that that is determined shall be done.
37 Neither shall he regard the God of his fathers, nor the desire of women, nor regard any god: for he shall magnify himself above all.
38 But in his estate shall he honour the God of forces: and a god whom his fathers knew not shall he honour with gold, and silver, and with precious stones, and pleasant things.
39 Thus shall he do in the most strong holds with a strange god, whom he shall acknowledge and increase with glory: and he shall cause them to rule over many, and shall divide the land for gain. (Dan 11:36-39 KJV)
This is where alien ufos back the new world religion with their technology, they are the "god of forces".
At the beginning of the final eschatological week, there is war in heaven and Satan and crew are cast out. Then the Antichrist rises and for the first part of the week he makes a covenant with all the religions of the world, Babylon the Great, who agree to follow him because he is doing miracles, and apparently the alien ufos are with him.
That is when Babylon falls into total apostasy from God, to profess faith in the Antichrist as God, and they all become "contactees," having familiar spirits, communing with demons, the false prophets of the antichrist spirits
KJV 1 Timothy 4:1 Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils; (1Ti 4:1 KJV)
KJV 1 John 4:1 Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world. (1Jo 4:1 KJV)
It is because Babylon has fallen and become the house of demons:
2 And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird. (Rev 18:2 KJV)
So the great delusion is the message the "god of forces" will bring with him, when Satan's stars (fallen angels) are cast out of heaven, and land on earth---as ufo aliens claiming to be a race of scientists who seeded life on earth and gave it its belief in God and the human soul.
THAT is the falling away that affects Christianity, Islam, Hinduism, Buddhism etc...they all see the aliens, and believe the earths religions are all obsolete...all sacrifice and offering to God ceases...the entire earth promises to follow the new gods whom their fathers did not know, the god of forces...the ufo aliens and their representative, the Antichrist, a human/angel hybrid possessed by the Devil.
They seek to change "times and laws", everything:
25 And he shall speak great words against the most High, and shall wear out the saints of the most High, and think to change times and laws: and they shall be given into his hand until a time and times and the dividing of time. (Dan 7:25 KJV)
But then the True God, jealous for His Name, will take them down:
26 But the judgment shall sit, and they shall take away his dominion, to consume and to destroy it unto the end.
27 And the kingdom and dominion, and the greatness of the kingdom under the whole heaven, shall be given to the people of the saints of the most High, whose kingdom is an everlasting kingdom, and all dominions shall serve and obey him. (Dan 7:26-27 KJV)