Every single character with DID I've ever seen has been represented as a serial killer. Some examples are Toko Fukawa from Danganronpa, Split(obviously), and Criminal Minds. (Theres also Fight Club, but I don't know if that could even be called DID as it showed up in the MC's 20s. I dont know what that would be called. However, I dont doubt it has added to the stigmatization.
There's no characters with DID that I can think of that isnt a serial killer. Is there a basis behind this? As far as I'm aware, serial killers with DID arent THAT common. So why is it so heavily represented and stereotyped?