I believe this is on-track.. without debating the finer points of the publishing industry, I would say this topic reminds me of "National Biscuit Company" creating products that can be stored and shipped across a continent, while every local town already had a bakery industry of some kind
Before Del Rey fantasy was fringe and hard to find (apart from Tolkien, obvs.) After Del Rey it was mainstream and a huge commercial success.
There was a post-Tolkien market slot and Del Rey filled it.
It was more innovation than invention.