“I have severe untreated mental illness and no grip on reality”
(Emphasis mine)
That is a vast oversimplification of how people work. It is absolutely plausible to me that someone might believe obvious lies but is otherwise qualified to drive heavy machinery. Analyzing the society you live in is a totally different skill than driving.
For example, if I found out my bus driver literally believes that reptilians run the world, I would still trust them to drive my bus because driving a bus has nothing to do with lizard people. Conversely, I wouldn’t trust a bus driver who agrees with everything I believe in but is currently having a panic attack.
This is important to me because I am mentally ill (treated, but mentally ill nonetheless) and autistic (which is treated like a mental illness), and this is the kind of logic that tyrants use to manufacture popular consent to further marginalize mentally ill people.