That doesn't make it mainstream. I used myself as an example as I consider myself a little more widely read than most Americans.Yeah, but that still puts the books in the top recognizable crust of fantasy novels. The percentage of the fantasy genre adapted into Disney movies is minuscule. As for your second point, that's personal. There are quite a few people young and old who respect and adore Newberry winners. It carries a lot of weight.
Heck, remember what it was like before there were LOTR movies?
"Didn't you read Lord of the Rings in high school?"
"No, I got laid in high school."