“And if the Taliban’s power was curtailed, so what?”
Oh, so your memory eludes you. Do you recall the Twin Towers attack that killed 3,000.
We went into Afghanistan to hit both AQ and the Taliban for letting them train and operate their as a save haven.
The mistake was not going there and hitting them, but not leaving after 6 months. Perpetual war is a delusion. We had every justification for going there.
The 9/11 terrorists were mostly Saudis, and no matter where they came from, if we had not allowed them to be here, they could not have accomplished their mission. No force in Afghanistan launched a missile or flew a bomber over to NY.