It doesn’t really. I mean Rule 34, you can manage to find some tiny amount of people actually attracted to a skelly body but it’s incredibly rare.
I first read about “anorexia fetish” from anachans who seem invested in the idea some men out there obsessed with skelly bodies and faux outrage about it. The media of course will repeat this for click bait articles but there’s very little evidence of people being sexually attracted to starvation bodies. What they point to sometimes as “anorexia fetish” is actually pretty generic S&M, misogyny, sadism, domination, deprivation, punishment, control type of stuff. Instead of bruises, whip marks, ball gags or chains the starved body is the signifier of the punishment or total control.
The only significant population that seem to have any appreciation of a skelly body are anachans themselves. If you want to find walls of photos showcasing starved female bodies going to anachan boards is easily your best bet and one of the only places to find them online. OTOH if fat bodies are what you want then you will find millions of porn and fetish sites dedicated to them.
I think because Anachans are really the only people who like anachan bodies they really want there to be a “anorexic fetish community” of awful creepy men lusting out of their emaciated bodies. It adds some needed drama to the tedious business of starving yourself and sharing tips on not eating. They love to hand wring and act outraged about it, but it comes off as hollow. I think they are a bit miffed that the only people who appreciate 3 inch thigh gaps and visible ribs are other anachans. Gets boring and insular, they’d like admiration from another audience.
It’s gotta piss off the anachans that they see thousands of websites dedicated to super fat women that men fetishize but almost no appreciation of “thinspo” bodies they admire.
Don’t get me wrong, there are definitely creepy dudes lurking the fringes of the anachan world but they are there because the girls are young and vulnerable or they are into sadistic shit, not because they find skeletons so hot. They are mostly sadistic pedo/groomers type creeps that know easy prey when they see it. If you are a pervert looking for vulnerable young women online then the anachan world is like shooting fish in a barrel.