The first diagnose of schizophrenia was in 1887, meaning that schizophrenia wasn't well understood or even known during ancient times.
Of course, the main symptom of schizophrenia are audiotory hallucinations, mainly hearing a "voice" speak to them.
Prophets common in ancient times such as Muhammad, Noah and The Temple of Apollo, all were given a message by a "voice".
Schizophrenia is poorly understood, including why patients hear these voices. What we do know is that the brain identifies this “voice” as different from the patient's own voice meaning that the patient simply doesn't talk to themselves.
Studies have shown that about half a century after the first diagnosis of schizophrenia, religion started to decline in popularity and less believed in.
What this means is either these famed prophets had undiagnosed auditory conditions or for the past one and half centuries, we've been trying to "treat" a message by a higher power.