My first inclination was that fractious parts of the Taliban were going to be responsible, but it does make sense that there are other actors out there who don’t want this to end (peacefully or otherwise). I hadn’t really thought about ISIS presence in Afghanistan, but they certainly wouldn’t be content to just let the US leave and it’s pretty ironic now that we are working with the Taliban, to deal with ISIS attacks.
With the US pull-out, the Taliban will be able to consolidate power in Afghanistan and the US will be able to commit more forces to rooting out what’s left of ISIS in Iraq and Syria. Certainly a strange bedfellows moment.