Another tweeted, "the committee doesn't even consider what dynamite means in terms of BTS's career vs rain on me for gaga's like that right there should've been your answer."
Had the award gone to BTS, it would have been a historic first Grammy win for the K-pop superstars.
J Balvin, Dua Lipa, Bad Bunny & Tainy's "Un Dia (One Day)," Justin Bieber featuring Quavo's "Intentions" and Taylor Swift featuring Bon Iver's "Exile" had also been nominated for the award that ultimately went to Gaga and Grande. Grande celebrated the duo's win for their dynamic duet, tweeting to Gaga, "eternally, deeply grateful for u, for this experience, to have been a part of this song and this celebration of healing and recovery, to be able to dance in the rain with u, to call u my dear friend & to now share this. beyond thankful. congratulations queen, ti voglio bene!"
"as much as i love ariana and gaga, this grammy should've gone to BTS and everyone knows it," a BTS fan chimed in, echoing what many other loyalists were saying. "they deserved this so so so much and it's so sad."
"what I’m most upset about is that they lost in a PERFORMANCE category...think what you want about the song but no one could out perform BTS," another supporter argued.
Putting a positive spin on the loss, ARMY looked ahead to the group's future potential accomplishments.
"Last year guest, this year nominated, next year we will win it," one fan predicted.
Meanwhile, BTS looked forward to what was still to come on Sunday night at the Grammys, reminding the ARMY to "Watch out for the performance!" with a tweet featuring a purple heart on Sunday night -- symbolizing their close bond with their fans.
See some of the reactions from the BTS ARMY below.