The tale of 2PM and 2AM are well known.
JYP fitted 2PM and 2AM against each other. He himself led 2PM, while Bang Sihyuk, better known Hitman Bang and later the boss of BTS, led 2AM.
2PM did better in the overseas, and while 2AM was a contender against SNSD in K-O-R-E-A, eventually SNSD overcame it and its position in K-O-R-E-A as the premier vocal act in there was overtaken by the person on the left of this post(I promise I won't mention her name on this post), who did defeat SNSD in late 2011, and after that 2AM fell into oblivion.
======
You can say what you want about how successful NewJeans was this year.
However, I have expressed concern that its popularity in K-O-R-E-A might hurt them.
Min Heejin, who developed NewJeans and Red Velvet before, is a witness of Red Velvet being grouped together with GFriend, whose ex-owner is now nominally responsible for Le Sserafim (although he holds little actual influence on how LS is run; LS is directly run by Hybe).
So it is basically a continuation of the fight 2016.
NewJeans collaborated with IVE, NMixx, Kep1er and ... Le Sserafim.
And the latter four received the Favorite New Artist Award while NewJeans didn't get anything.
This MAMA was given in Japan where LeSserafim, because of its popularity in there, has a huge advantage.
And NewJeans showed their disadvantage against LS and other acts by being grouped with them while not winning an award. Whatever they might win tomorrow does not matter because they were, well, not considered to be up to speed with the other 4 acts.
I think Min Heejin might have made a mistake by putting NJ to there with the other 4 acts who won something, although it might not be her who made the decision. Being classed with them is something, and being shown to be not of the same level as the other 4 who were in the same level was, I would say, quite painful.
Already some Bunnies are afraid that LS would overtake NJ in the overseas, where the money is. LS's superiority in Japan, due to its 2 Japanese members (1 quite known) 1 IZOne member and 1 PD48 contender, is hard to assail in there; NJ has to make it up from its popularity in other countries, and its great success in K-O-R-E-A, which doesn't really mean anything as far as revenue is concerned, might hold it there and not being able to compete against LS in the overseas.