The US and UK were actually quite happy with the Shah they installed, he allowed western access to Iran's oil.
Edit: the post I'm replying to has been heavily edited.
https://en.wikipedia.org/wiki/History_of_Afghanistan#Contemp...
The taliban came to power by stopping socialist massacres, most famously in a "torture prison" the socialists built. That is what made people choose their side. They killed less people in open warfare than socialist revolutionaries did in peacetime, and much less than the Soviets did when "helping the socialist revolution spread".
Despite what happened since, sadly, I think you'll agree things never got as bad in Afghanistan as they did during the socialist revolution they had there. Not even now.