Funny thought ran through my head. When Obama pulled troops out of Iraq during the power vacuum going on in Syria, ISIS came to be in a very similar fashion as these weapons seemingly being left to the Taliban.
However, maybe I'm optimistic. China says they might be trying to make inroads to exploit Afghanistan, but an armed Taliban, provided they somehow remain on the level, would be quite the obstacle to Chinese dominance of the region. As some of you have said: it's the "Graveyard of Empires." Even if China were to get particularly ruthless, so would the Taliban. Gloves off, they both kill each other, as long as the USA does not get involved again. Emphasis on not getting involved again.
Shit, another funny thought ran through my head. Surely Afghanistan and other Arabic countries are well aware of what the Chinese are doing to the Uighurs. That's an even bigger source of resentment the Taliban could in theory have towards China. This is weirdly exciting in a grand strategy sense.