Grimes fans DON'T act like that. Florence fans do that.
I saw Grimes at 930 club in DC and everyone was making furious attempts at movement or dancing depending on the space available.
The problem is not unique to Florence, it's a rock thing. Florence is not even "indie" but she's basically rock in the audience she draws from, from what I hear. The radio or websites that talk about Florence are aimed at the rock listener. So it ends up that her fans are that. And especially bad in her case as they are a bit older, not even the "hippest" rock audiences (because Florence doesn't get acclaim from Pitchfork and such) who would at least respect the concept of dancing even if they don't dance. Florence fandom is a more conservative rock audience that might ignore dance music and hip hop entirely. unfortunately rock audiences became opposed to dancing several decades ago for various bullshit reasons related to racism and classism and sexism. It doesn't even matter how dance based the music is, or how frustrated the artist is that only the artists on stage are moving. These fucking rock audiences are "kids still standing with their arms folded tight." I saw Atoms for Peace live once which is a Thom Yorke dance-rock side project and nobody moved at all except Flea (bassist) and Thom himself. and not cause the music sucked. I bet even at LCD soundsystem shows nobody dances (and again- not cause they suck- sorry james brooks).
the not-dancing part of indie and rock culture is fucking bullshit and even promotes terrible conservative ideologies because it promotes fear when people just stand there. if not now, when? if you're not fucking moving your ass while listening to (feeling, physically in your bones) the bass of venus fucking fly in june 2016 then... really WHEN are you going to start acting alive rather than promoting death ideologies, motherfuckers.
and it really hurts her i think to have nobody moving at all... that is why she changed her whole style of music starting with darkbloom because the early music she was doing was not promoting good vibes at her shows. she gets stage fright and if nobody is giving anything or dancing or opening themselves up and being vulnerable, if they're only just staring ar her singing from her heart and being a spectacle on stage for them, that has to be so fucking alienating and horrifying if she stops to contemplate that even for one second, and maybe today she was going through enough other shit that she stopped to think those dark thoughts about why am i even on this stage if you guys are giving nothing, and so she left.