Defeated how? It spent less time at #1, it has less uls, streams and digital score and its not even in top 100 today, while lwa is still in top 25. The song is good but its bascially a viral hit with with seemingly not much longevity.
But there are other bigger songs this year that beats out both so
The thing with IU is the consistency, its not that she have the top song of the year every year.
And in Korea in specific, older audience mainly listen to trot. It's a whole demography that only focus on that, that's why we had the same song topping the Gallup poll for the 40s+ for 3 consecutive years now, let's not even talk about the artists... they listen all the time the same artists and music.
The below 30s rank is the most accurate way to measure real popularity, the other one is barely going to change in the following decade. Obviously IU stands out making it quite high even among the older audience, she's the singer of the century in korea, but she's an exception, not the rule.
Yea, the whole reason they started splitting the group into 10-39/40+ in 2020 is because the trot artists were starting to take over the top 10 every year, because while the younger generations have hundreds of artists and songs to choose from, the older generation have 5-6 popular trot artists and a handful of songs which made their vote weight that much higher and the rankings didnt make much sense because of it.
One can also see the trend with IU moving up higher in the older brackets as the years go by, in 2030 its likely she will start topping the 40/50 age bracket while going down in the teens bracket. What people listen to in their youth is what they will stick with and the discovery of new music basically stops dead in the 30's for the wast majority of people.