The article suggests lack of oversight from TSR on the Japanese market's needs is mostly to blame. They kept making products released much later than their NA counterparts, with half-hearted support, in packages that were more expensive than the competition. In fact, by being difficult with Group SNE, they actually created a competitor(Sword World RPG). That's no way to win a market!

I believe the core of it actually comes from the different approaches to media publishing that took hold back in the 1970's: US markets became very keen on going upmarket with more expensive products and big-budget franchises: that became the strategy to get positioning at retail. Japan's pop media, on the other hand, has been nearly synonymous with manga magazines and light novels, which are centered on individual authors and offer more opportunities to showcase work in anthologized and serialized formats. TSR's competition in Japan were churning out cheap books and magazine articles that made tabletop gaming accessible to a casual fan, while D&D had the big boxed sets, the special dice, the miniatures, etc.