I don't think everyone is. I still don't think it's a great single choice, but the video slays (I love it). It's got replay value. Birthday is a better song, but the video was lacking and too long. Hope this does well.
Who started hating Birthday after it underperformed? I haven't noticed a sudden increase of hate towards the song.
It's also about a month too early to accuse people of only being fans of this song because it's smashing, but whatever floats your boat I suppose.
I remember it was loved by almost everyone and they wanted it as a single, maybe it wasn't that noticeable but after it underperformed it was suddenly not a good song or not a good single choice.