"Some Afghan guy keeps ringing our office, so I blocked his number"

Explanation: In the lead-up to 9/11, the CIA received several credible reports that Al-Qaeda, radicalized by (checks notes) the Saudis letting US troops station in the sacred territory of Saudi Arabia during the First Gulf War, were planning an attack on US soil. One of the warnings came from Ahmad Shah Massoud, the leader of the Northern Alliance fighting against the Taliban in Afghanistan, who noted that his own intelligence networks had upturned talk of an attack from (allied to but separate from the Taliban) Al-Qaeda.

On one hand, the CIA deals with a lot of foreign actors making threats, few of which end up amounting to anything; and even those threats which are credible are not always immediately identifiable in route, method, timing, etc.

On the other hand, to anyone who is aware of the CIA’s long history of incompetence and failures instead of just the image of the shadowy all-powerful intelligence agency, it’s just as likely that the CIA dropped the fucking ball - or those officials in the Clinton and Bush administrations who received the CIA reports dropped the fucking ball.