Both Dick's and Walmart stopped selling "modern rifles" strictly due to politics. That category is outselling all other long guns, I'm pretty sure. Even if not, it is a very good profit generator.
Sportsman's Outdoor Superstore (a direct competitor to Dick's) is kind enough to publish sales rankings:
https://www.sportsmansoutdoorsuperstore.com/best-selling-guns-2017/
An AR is #3, behind two pistols.
Dick's management were fools, the move to stop selling AR type rifles alienated a very core customer segment - and one that complained loudly and then voted with its wallet.
I think Walmart was forgiven to a much larger extent because firearms are a small part of its business. Still a shame though...
