Singers come in all shapes and sizes. I don’t know if there are any physiological advantages related singing ability and height or weight, but is it possible that you aren’t used to larger women being famous or celebrated? There is a lot of societal pressure on women to be slim and attractive (and young and demure, but also intelligent and sexy, but not in a threatening way, just enough to know she’ll want to have sex, but then be ready to stop after the man finishes). Singers, meanwhile, are “permitted” to be any size (although being sexy helps record sales).

Edit: Oh foop, I just realized which community this is.