In general music consumption in Korea is just on the floor right now. And as you mentioned, the fact that we've had comebacks from artists who earlier this year dominated the charts and together represented a peak in music consumptio, makes the situation even weirder. It's as if the listeners that were so into them suddenly disappeared or aren't paying attention. Can't really think of any external reasons that might be related to that. It's also not just something occuring for a week, but something that kinda already started in July. It's unexplainable to me.
In the world you mean, Billboard Hot 100 #1 is now reaching a new record for lowest points for top spot.