Why not both? Ted Kaczynski was an important thinker whether or not you agree with his thesis and methods. ISAIF was published in newspapers and the sky didn't fall.
I tried to read Kaczynski's manifesto once and came away with the impression he was mentally ill. I think there's stuff in there that impresses people with personality types who are disposed to agree with him, and it sounds cogent to those people, but I found it hard to escape that he was pretty incoherent and made logical leaps into a private reality.
I can't recall the details, but I saw a documentary that made me doubt that the mkultra experience was very formative for him. Iirc he had a big change in his outlook and demeanor at around the typical age of onset for schizophrenia and similar issues. According to what I've read, these conditions seemingly have multiple causative factors within an individual, genetic and environmental, where "environmental" factors can include stuff that started in the womb.
I think his ideas come across more clearly and coherently in his later work than in his manifesto, but that's often the case.
I don't regard him as a philosopher but rather an agitator, not unlike Thomas Paine or (insert your preferred historical figure here). This largely because his writing is not in a spirit of inquiry over where technology might go, rather it is conclusory - industrialism is path-dependent and net negative, with the only open questions being how to undermine it effectively.
His works read like a book-smart guy that thought his intelligence in X field translated into intelligence at large. It didn't, and frankly his actions were so illogical and nonsensical that it's a puzzle why people think he is some sort of misunderstood genius.
He's no different than the many, many cranks writing ill-informed manifestos online.