If by "main fandom" you mean the fandom that's usually focused on series with slashable pairs/groups of dudes...MCU, Inception, Teen Wolf, Supernatural...then yeah, YoI is the kind of anime that's gonna sweep it. Didn't that happen with Prince of Tennis back in the day?

The canon gay definitely helped. And I think it also got a boost from having characters that were explicitly from so many different countries, so people got to see their ethnicities and heritage celebrated in a way that a lot of shows don't go into. Steven Universe is big for similar reasons. (Although probably not with MCU-type fans? That's an impression, not a scientific survey. I know it's popular with mahou-shoujo fans.)

The animation just made me really sad that Crystal couldn't have been this good. You watch the skating routine sequences, with all these lovingly animated muscle movements, even the motion of the hair, chests heaving as they try to catch their breaths afterward...and compare that to Crystal's "let's crop the frame as awkwardly as possible so simple actions happen offscreen and we don't have to draw them" and "all you get for this action moment is the camera panning across a dramatically-posed still"...it's kinda soul-crushing.