The origins of teratophilia are not entirely clear, in spite of it getting so much traction online. Entire subfields of psychology are devoted to the study of human sexuality, yet its sheer variety remains something of a mystery.
That said, it’s worth looking at some of the different explanations that people have used to understand (and in some cases defend) teratophilia.
Subversion of Beauty Norms
Teratophilia gives some people an outlet to experience sexual gratification outside of conventional societal standards. By focusing on strange creatures or on people with physical abnormalities, they can practice finding beauty in unexpected places.
A Way to Process Shame
In psychoanalysis, the variety of psychology developed by Sigmund Freud, sexual attraction often involves the interplay of conflicting emotions, many of which are rooted in early experience.
A person who has a negative formative event involving physical abnormalities might find themselves dealing with those negative emotions through their adult sexual life. They might develop an attraction to those who an unaccepting society would label as physically deformed people.
An Alternative Outlet
Some people consider attraction to certain stereotypically masculine characteristics — such as aggression and domination — to be problematic.
The attraction to monsters such as Bigfoot could allow people to indulge in an escapist fantasy, one that has male aspects but is free from associations with patriarchy or personal trauma.
Biology
Some evolutionary scientists have speculated that teratophilia might be an updated interpretation of certain mating rituals.
Many of the scenarios in popular monster erotica involve creatures with exaggerated abilities of strength and sexual prowess, which could, in earlier human settings, be seen as markers of biological suitability in a mate.