Without going into all the verses we're going to talk about strong delusion. Paul said these people did not receive the love of the truth. Consequently, God would send on them a deluding influence that they may believe what is false. God is permitting the "delusion” to take place. ‘They perish because they did not accept the love of the truth. For this reason’ they experience delusion. As in Romans 1:24–25 (‘God delivered them over … They exchanged the truth of God for a lie.’) The delusions certain people experience reflect God’s response to a prior decision on their part.
During the first century there was a 'great apostasy' happening because Jesus failed, to do what they expected of their Messiah. Many did not believe Jesus was the real Messiah in prophecy and were going apostasy. Israel wanted her types and shadows to be fulfilled in a literalistic or a nationalistic manner being blinded by the earthly or carnal system of Moses.
"In classical Greek the word apostasia denoted a political or military rebellion; but in the Greek Old Testament we find it used of rebellion against God 1 Samuel 8:7, and this becomes the accepted Biblical usage. Paul's thought is that in the last times of the old covenant there will be an outstanding manifestation of rebellion against God.
Because of this rebellion against God and willful belief that the Messiah was going to restore the kingdom in a literalistic or a nationalistic manner God send them a strong delusion, that they should believe that lie.
How was this strong delusion sent by God accomplished? The Jews foolishly believed the time had come for them to “throw off the Roman yoke” and thereby establish the kingdom they thought was in their prophecies. This proved to be Israel’s complete destruction.
Rome did not initiate the war against Jerusalem. Jerusalem was under the authority and control of Rome. Headstrong men in Jerusalem itself believed the time had come to throw off the Roman yoke. They kept irritating the people and inciting them to rebel against Rome.
In November of 65 the great Jewish revolt against Rome broke out at last. The people quit paying their taxes. This would have been sufficient in itself to cause Rome to turn against Jerusalem. Jewish Zealots had driven all Roman forces from Jerusalem and had actually slain more than 600 Roman troops.
Agrippa appealed to the people of Jerusalem to be mindful of the great multitude of nations that were already living peaceably under the authority of Rome with no intention of rebelling and should Jerusalem as one nation, take up arms against the mighty Roman empire?
Agrippa temporarily stopped the Jewish revolt against Roman that was threatened, and the people started again paying their taxes. But that peace was short and time provide a fulfillment of Agrippa warning. Feeling kept building up and the war was on its way. (Josephus, p 1870)