Shocker. You mean to say that the market with more people is bigger?
This will stay the same it always goes with Japanese companies. They make products exclusively for the Japanese market, and any sales they get outside of Japan are just a financial bonus.
If something performs really well in Japan but badly everywhere else they keep making it and just don’t distribute globally. If something performs really well globally but badly in Japan? Cancelled.
Rap was extremely popular in Asian countries, especially Japan and South Korea, in the early 2000s. I don’t know if it has remained as popular as back then though.