I was at chapter 17ish and I reached an enlightenment.
The setting here is literal hell. Everyone is either evil, retarded or abused. No sane person can ever exist here. Its impossible. Even I as a reader feel like I'm going crazy with each next chapter. Its like I'm reading some lovecraftian forbidden texts that sap my sanity.
Hence only the doomguy can exist here. Someone who can share qualities of locals while at the same time does not belong. Mc became the doomguy.