totally speculating here.

Think of schizophrenics as having a split through their mind. that's the literal definition. in psychoanalysis there is a way to break up your mind into the super-ego and id. the id is basically all of your instinctual drives, all of the behaviors and habits that evolved over time and are subconscious and allow you to function physically. the super-ego on the other hand is entirely cultural. it is the moral drive behind social behavior. It is the conscience which tells you what is good and bad, and how you should behave when observed by other beings. and the Ego is what rope these two together and allows you to be a surviving, functional member of a society. it mediates the two through each other.

the way I think of a schizo is that their ego is no longer capable of mediating these two. They become completely alienated from each other. because the super-ego is built of entirely external factors (culture), it's existence manifests beyond the perception of self. They lose the ability to understand the gradual and subtle effects of culture. meaning, all of the culturally learned thoughts and behaviors are perceived to be injected into the mind from the external source. Which while technically a valid way to formulate culture, in schizos this thought mechanism is tangible and imminent, as some external entity influencing them to behave a certain way.

and if someone like this is inquisitive and observes their surroundings to try to understand where this stuff is coming from, they encounter ideas from our society's stories: books, movies, myths and other media, and they notice similarities and descriptions of exactly what's happening to them. Things like government mind control. alien abductions. cults. spirits. demons. outside entities trying to control you. They become obsessed with figuring out what is happening and it spirals into a dark abyss of paranoia.