Both sides of this argument are being incredibly obtuse and annoying.
Acting like Twice had no competition is just plain stupid. I'm not going to mince words here. Not one, not two, not three but four other girl groups scored a Perfect All-Kill on the charts in 2016 (Mamamoo, BlackPink, GFriend, IOI).
If you weren't actually around for the 3rd generation girl group war, then don't speak on what you don't know. The other girl groups didn't just roll over for Twice, and at least digitally, competition was fierce, even if Twice was the clear leader.
But what's also disingenuous is acting like Twice was miles ahead of the other girl groups. They were the obvious top girl group in K-Pop at their peaks, but they didn't lap the competition many times over.
Even in 2016, I distinctly remember fierce arguments in discussing Rough vs. Cheer Up (Twice vs GFriend), and yours truly was personally involved in any discussion that involved Mamamoo. I have the battle scars to prove it.
Do not treat Mamamoo like an after-thought. They were huge in their peaks too, and the Korean public loved them. For example, in 2016, their episode of SNL got even higher ratings than Twice's. Which kind of goes back to both of my points.
Twice had plenty of competition in their peak. Their top girl group spot wasn't just handed to them.
AND
There wasn't that big of a gap between them and the other top girl groups. The gap was definitely biggest overall in 2016, but come on.