The attack was claimed by ISIS-K - a foreign fighter offshoot/offbrand. Funny thing is that ISIS-K fighters were getting lifts from American chanook helicopters in Afghanistan and is largely made up of US assets and/or people formerly trained by the US in Afghanistan.
Lots points to it being a CIA asset, tldr. They’re a dirty army that can be used to keep an area distabilised or prevent other geopolitical powers from building infrastructure/influence (the nutshell purpose of ISIS-K, particularly in Afghanistan to prevent pipelines being built).
They had the inside scoop on an attack outside any usual operating theatre by a group with tangible links to US cooperation/orientation? No kidding.