Do you think that GRR failed to pay enough attention to religion as a political and cultural factor in the earlier books, so he had to rush bringing it under the spotlight for AFFC? He wouldn’t be the first fantasy author to underestimate the role of religion in a medieval setting, so it’s weird to see him falling in one of the most common clichés of the genre.

I don’t think that’s actually the case. I would argue that we see GRRM laying the groundwork with the street preachers who turn up in King’s Landing in Tyrion V and Tyrion VI of ACOK, and the way they prefigure the riots that explode in Tyrion IX and literally rip the corrupt High Septon to pieces. 

What I would say is that I think GRRM missed a trick by not having the religious element be there in the background in ASOS. Now, there are good reasons why that’s not the case – ASOS is a massively over-stuffed book already, with more chapters than any other book in the series – but I do think he could have had some background elements when Jaime and Arya are criss-crossing the Riverlands, or on the streets of King’s Landing with Sansa and Tyrion.