The soviets lost because the afghan socialists were trying to do atheism in afghanistan

That wasn’t the only issue, and the soviets told them to not do that anyway. State atheism is just an easy scapegoat.

Edit: And anyway, if we’re going to look at the history of communist movements. Not one has ever managed to maintain a fruitful relationship with religious authorities no matter how many concessions they give. State atheism is a necessity for any real communist movement at some point.