The amount of people I see trying to convince me that the Billboard 100 Japan doesn't matter and that being successful in Japan is no big deal is honestly kind of funny. Like sweetie, "Twice is only popular in Japan" is not the insult you think it is. Japan has the biggest music market in Asia and is the second biggest in the world. Multiple huge western artists like Rihanna and Little Mix have been trying to break into the Japanese market for YEARS and even have Japan exclusive albums or Japanese versions of their songs. Right now, Twice is the only female K-pop act with any kind of longevity in Japan. They still get chart topping hits over there to this day. 'The Feels' peaked at #3 on the Billboard 100 Japan, what other Korean girl group can do that after 6 years.
You can tell it's the jealousy, because if their favs entered the Billboard Japan top 10 every year, they'd never shut up about it.