JRPGs, in general are considered quite niche in the gaming market, and only a few actually break out of the chain and went mainstream. Persona, Final Fantasy - which has always been a mainstream games - and NieR. These particular titles have higher budget than the regular JRPG.

I would say presentation is just as important, which most of JRPG are lacking, be it marketing and visual quality. This is due to the usual lower budget for JRPG. It's only normal for people to get attracted to visually impressive products. As an example, try comparing God of War Ragnarok trailer to just any JRPG trailer, you could tell the end-products quality differences. That could be the reason why Western Triple-A titles sales are higher than the usual JRPG.

Based on my experience with some of the so-called mainstream JRPG titles, they do stands out among the other titles that shared similar tropes. Take P5 as an example, this game feature a very impressive visual design. From the presentation to the artstyle and Gameplay; the UI really made the game stands out a lot. It's not very often that you could come across product with such quality. The marketing behind - although questionable at time - did help the game a lot.