US forces may not be leaving Iraq or Syria, but there aren’t a lot of ISIS targets for them to hit anymore. This has led to a precipitous decline in the number of US bombs dropped on those two countries, and has the military’s priorities shifting eastward, to Afghanistan.
ISIS has lost virtually all of its meaningful territory, and to the extent the group’s forces have fled into the desert, they still aren’t convenient targets for US warplanes. In Afghanistan, the US-backed government controls only about 50% of the territory, leaving open a lot of enemy territory to target.
In recent decades, the Pentagon has kept Afghanistan in its back pocket for when things slow down elsewhere. When the 2003 US occupation of Iraq slowed down, a surge was announced in Afghanistan. When the ISIS war in Iraq and Syria ratcheted up, Afghanistan was on the back-burner, but now is facing a new escalation.
Unlike ISIS, where their control over territory was always very tentative, the Taliban has a lot of territory in Afghanistan which they have a long-standing stranglehold on, and where they won’t be readily displaced. This makes Afghanistan every bit the long-term project it was 17 years ago when the US invaded.