They made war on Afghanistan. Then they gathered up all the wreckage from the towers and got rid of it before anybody could investigate.
There are so many versions and opinions that you really need to search published news stories for material. No theory that makes sense has been offered yet.
However way they responded, it didn't stop the threat of terrorist attacks. That is something that is beyond human ability; however, the Bible says that God will not allow the earth or life on it to be damaged beyond repair. In fact, the Bible promises that God will “bring to ruin those ruining the earth.” (Revelation 11:18) By means of his Kingdom, or heavenly government, Jehovah will cleanse the earth of wickedness and bring about the conditions he originally purposed. (Genesis 1:26-31)
Psalm 46:8, 9 promises us about God: “Come, you people, behold the activities of Jehovah, how he has set astonishing events on the earth. He is making wars to cease to the extremity of the earth. The bow he breaks apart and does cut the spear in pieces; the wagons he burns in the fire.”