I don't remember him writing about strongly believing in astrology or UFOs. I also don't think him using drugs, even enough to "forget ... what a poem was" to bear on his AIDS-denial claims. What I (previously) found plausible was that he claimed to be unable to find the original research providing evidence that HIV causes AIDS and he also claimed that viruses like HIV are incredibly common and thus unlikely to cause AIDS. Coming from a Nobel Prize winning biochemist, and also being unable to find info about the aforementioned original research, I concluded that his claims were plausible.

Note that I was a teenager at this time, I had not yet been exposed to Bayesian probability, cognitive biases, or any kind of systematic info about rational thinking beyond Feynman books and similar pop-sci books.

I think of myself as relatively intelligent, so I was merely pointing out that reading about AIDS-denial by Kary Mullis was not "positively crazy".