"Although it isn't entirely clear what Trump is saying, the Saudi-born militant Osama bin Laden and his Al-Qaeda terrorist network are widely considered to be the culprits behind the attacks."
Despite this, bin Laden himself denied all involvement on several occasions before his death in 2011.
Then Bin Laden should not have taken credit for it and bragged about it: Pentagon-Released Video of Osama bin Laden Talking About Terrorist Attacks B.
Skip to 50 seconds: "UBL: (...INAUDIBLE...) We calculated in advance the number of casualties from the enemy who would be killed based on the position of the tower. We calculated that the floors that would be hit would be three or four floors. I was the most optimistic of them all. (...Inaudible...) due to my experience in this field, I was thinking that the fire from the gas in the plane would melt the iron structure of the building and collapse the area where the plane hit and all the floors above it only. This is all that we had hoped for."
That sounds like a confession to me.
Engineers would disagree.