While I pin the fault of Jacob being a narcissistic sociopathic douche on him and him alone he didn’t become a conspiracy theorist out of nowhere. He became one in response to seeing the owl beast in the middle of the woods at night alone.
Could you imagine how traumatizing that experience would be? A giant hostile creature that you’ve never seen before just shows up one day in the woods. Jacob was lucky enough to make it out physically unscathed, but that experience would have left deep mental scars. And what’s worse is that those mental scars were left untreated because he never got any closure, or any explanation for what happened. And the thing about untreated scars is that they get infected. So his psyche was infected with a deep fear of the unknown, and of dangerous creatures lurking in shadows beneath the watch of humanity.
How he coped with that trauma was undeniably wrong, and it would be wrong to say that all of his actions stem from his trauma as his actions are very explicitly driven by narcissistic and sociopathic tendencies. But I nor pretty much anyone else on this planet could go through what Jacob did without becoming at least somewhat like him.
I think if you were to strip away the conspiracy theories, the desire for fame, and everything else you’d be left with a fearful and broken man trying to give himself some semblance of an explanation as to what happened to him one very bad night.