They didn't.

Afghanistan was governed by the Taliban. The attack was carried out by Al Qaeda, a predominantly Pakistani-led terrorist group.

Afghanistan was invaded because Bin Laden was known to be in the country, and the Taliban refused to hand him over to the US on the basis that they wanted him tried in an Islamic court. They offered to try him themselves, or send him to Pakistan. The US wasn't satisfied with this, so invaded, and in a matter of months, it became clear that Bin Laden had fled to Pakistan.

So Bin Laden was in Pakistan, with the support of a predominantly Pakistani-lead terrorist group, but the US didn't invade Pakistan like they had invaded Afghanistan. And Iraq, at this point. Because why not invade Iraq? They've got absolutely zero to do with this, but sure.

But still no invasion of Pakistan. Even though Al-Qaeda's there, along with Bin Laden. Why not? Why? Probably because... Pakistan has nuclear weapons.

The official whodunnit for 9/11 is that a rich guy from a prominent Saudi family lead a Pakistani terrorist group from some place in Afghanistan. The US mainstains an alliance with the Saudis, a state of limited cooperation with Pakistan, and Invaded Afghanistan - the one with the absolute weakest military.

They didn't.

Afghanistan was governed by the Taliban. The attack was carried out by Al Qaeda, a predominantly Pakistani-led terrorist group.

Afghanistan was invaded because Bin Laden was known to be in the country, and the Taliban refused to hand him over to the US on the basis that they wanted him tried in an Islamic court. They offered to try him themselves, or send him to Pakistan. The US wasn't satisfied with this, so invaded, and in a matter of months, it became clear that Bin Laden had fled to Pakistan.

So Bin Laden was in Pakistan, with the support of a predominantly Pakistani-lead terrorist group, but the US didn't invade Pakistan like they had invaded Afghanistan. And Iraq, at this point. Because why not invade Iraq? They've got absolutely zero to do with this, but sure.

But still no invasion of Pakistan. Even though Al-Qaeda's there, along with Bin Laden. Why not? Why? Probably because... Pakistan has nuclear weapons.

The official whodunnit for 9/11 is that a rich guy from a prominent Saudi family lead a Pakistani terrorist group from some place in Afghanistan. The US mainstains an alliance with the Saudis, a state of limited cooperation with Pakistan, and Invaded Pakistan - the one with the absolute weakest military.