I would suggest there is a subtle phenomenon at play. Roughly speaking, a portion of the population is "wired" quite differently than the rest, and they function in the world very differently than anyone realizes. Put bluntly, they are more robotic and absorb directives from those they consider "authorities".

"They" are well aware of this and implement their programs based on it. They carefully disguised it by giving these people relatively reasonable "orders". Over time, as "They" have started to lose control, they needed to issue increasingly less reasonable orders, and this is manifested as "mental illness".

So suppose you come across Lt. Cmdr. Data beating some human to death. Is the relevant question, "Why is he so mad?" Not at all. Data is as he always ways, a robot. You would ask, "Who programmed this behavior into him?"