I've seen the large dog trend coming for a while. Not just the large and giant breeds, but large and giant dogs in general. All the over-sized Sibes, Rotts, GSDs, Labs, and who knows what else. Then people got wind that large dogs are easy dogs, and that isn't really true. Let alone the temperament problems, health issues. BYB'ers picked them up. It's only been growing since. For most of the general public, a poor tempered dog isn't a big deal. You just throw them in the backyard, right? Go and get a new puppy.
It's just another trend. There's several in my area.