Obviously doctors didn’t catch the problem, so his family probably had some warning signs, but that’s about it. His most obvious symptom was severe migraines. About 6% of American men have migraines (about 18% of women). So it’s not enough.
The paranoia is possibly more diagnostic, but as a condition itself, which could be by itself, or associated with schizophrenia. But that still needs a professional diagnosis early on.
This was probably a bolt from the blue, that nobody saw coming, so nobody did anything to stop it.
Someone did something to stop it. You better believe.