"11 And for this cause God shall send them strong delusion, that they should believe a lie:"
https://www.biblegateway.com/passage/?search=2%20Thessalonians%202:11&version=KJV
"The Bible makes it clear why God is sending a strong delusion in the end times: “They perish because they refused to love the truth and so be saved. For this reason God sends them a powerful delusion so that they will believe the lie and so that all will be condemned who have not believed the truth but have delighted in wickedness” (2 Thessalonians 2:10-12). Simply put, God sends a strong delusion to those who choose not to believe the gospel of Christ. Those who take delight in mocking and rejecting Him, He will condemn."
https://www.gotquestions.org/strong-delusion.html
"We know that the events surrounding the end times, as described in the Bible, will include a powerful deception (Matthew 24:24; 2 Thessalonians 2:11). Recently, interest has been rising in the theory that this deception will include alien beings supposedly from another planet."
https://www.gotquestions.org/alien-deception.html
"A delusion is a strongly-held or fixed false belief that conflicts with reality."
https://www.verywellhealth.com/delusions-5113070