Before I pursued a doctorate in STEM profession, I was the charge nurse of a psychiatric unit. The many schizophrenic patients with whom I engaged would have been completely incapable of writing a manifesto or planning an assassination.
My assessment:
This man is not schizophrenic, even if his lawyers claim that he is.
I don’t think he’s mentally ill either. He’s so propagandized he’s lost his grasp of objective reality, which may look like schizophrenia to some. One of the chief aims of propaganda is to get people to do things they normally would not do.