So my theory is simply this:
Then the lawless one [the Antichrist] will be revealed and the Lord Jesus will slay him with the breath of His mouth and bring him to an end by the appearance of His coming.
9 The coming of the [Antichrist, the lawless] one is through the activity of Satan, [attended] with great power [all kinds of counterfeit miracles] and [deceptive] signs and false wonders [all of them lies],
10 and by unlimited seduction to evil and with all the deception of wickedness for those who are perishing, because they did not welcome the love of the truth [of the gospel] so as to be saved [they were spiritually blind, and rejected the truth that would have saved them].
11 Because of this God will send upon them a misleading influence, [strong delusion] so they will believe the lie,
12 in order that all may be judged and condemned who did not believe the truth [about their sin, and the need for salvation through Christ], but instead took pleasure in unrighteousness. [amplifed version]
--- 2 Thessalonians 2:8-12 AMP
God is giving them what they want.
These are people who have not only heard the truth and rejected it but
"who suppress the truth by their wickedness," (Romans 1:18)
In actuality, they are deluding themselves, and God allows them to believe their lies with all their hearts.
When we hear truth and obey it, wisdom and insight comes but when we hear truth and disobey, foolishness and folley are ours.
The Coming Delusion in the End Times
There has always been much speculation about what this delusion will be.
The strong delusion in verse 11 references idols or little gods and is found several times in Jeremiah:
Jeremiah 10:14-15, Jeremiah 51:17-18.
But perhaps the most revealing reference comes from 1 Kings where
"The Lord said, 'Who will entice Ahab to go up and fall at Ramoth-gilead?' And one said this while another said that. Then a spirit came forward and stood before the Lord and said, 'I will entice him.' The Lord said to him, 'How?' And he said, 'I will go out and be a deceiving spirit in the mouth of all his [false] prophets.'" --- 1 Kings 22:20-22
I believe this
1 Kings 22:22
verse forshadows the great deception coming in the end times and I believe it will be in the form of lying spirits.
But perhaps the strongest (and a second witness) reference comes from
1 Timothy 4:1
"Now the Spirit expressly says that in later times some will depart from the faith by devoting themselves to deceitful spirits and teachings of demons,"
And the Apostle Paul adds clarification to this when he cautions,
"But even if we or 'an angel from heaven' should preach to you a gospel contrary to the one we preached to you, let him be accursed."
Galatians 1:8
Moreover, we know that Satan comes as an angel of light:
"And no wonder, for even Satan disguises himself as an angel of light."
--- 2 Corinthians 11:14
A fallen (demonic) angel will come, perhaps in the form of an extrateresteral being (ufo being), and will give a gospel contrary to Jesus Christ.
Sadly, many will believe this false gospel.
And this demonic false gospel along with persecution of those who believe Jesus Christ will cause most to
deny the Lord and abandon the faith.
But remember what the Apostle John said,
"These people left our churches, but they never really belonged with us; otherwise they would have stayed with us. When they left, it proved that they did not belong with us." --- 1 John 2:19 NLT
And so, the end result will be the purification of the church, demonstrating that
what Satan means for harm, God means for good.
(Genesis 50:20)