I need to be careful how I say this, but in the early 00's (as we were supporting some austere ops) in the region, I was surprised to learn of some under-the-radar cooperation between Iranians and Americans in Western Afghanistan. This was linked to Iranian concerns as regards Taliban and Sunni activism at the time. (And I think that's about as far as I can to with that).
No love lost between the Taliban and Iran then, nor now, it seems. (Though the story in the link by Asturius56, thank you, paints a more nuanced picture of that relationship ...)
That thread - thanks ORAC - as regards water rights, drug trafficking, and the economic challenges in that border region ring true.