I don't really see people who fetishize it unless they are doing it maliciously ((which tbh I haven't seen at all)) but I've definitely seen people infantilize people with autism thousands of times.
There was a pretty big tiktok account ran by a married couple where people called the husband a pedo 'cause his wife was autistic and would act like a giggly, overly-excited child around him. It hurts seeing someone who is just genuinely in love and comfortable around another person be victimized and their partner demonized 'cause people can't get their heads out of their hampster holes.
And it's happened with me with past partners. It doesn't feel good having strangers say shit about you thinking they are some sort of savior.
People here need some literacy skills fr, he is NOT a literal child, he is hundreds of years old, it's not like his physical body transformed into a child that would be different. I see it as that monster self is just extremely naive, shy too, and he has childish hobbies (like videogames)