It's kind of grimly fascinating watching his descent. He's always seemed like a dick, but he's definitely gone downhill from pub bore to full-on conspiracy theorist. Is this what fame does to you? Or is this what happens if you stay in the echo chamber for too long?
It's partly the latter but there's a bit more too it as well.
It's also that after their initial incident/talking point that gets them some recognition and a following, they then become incentivized to further appeal to their fan base/following. So with Fox he made his comments on Question Time (which were innocuous compared to his more recent stuff). This led to him getting some exposure in that sphere (cynics, right wingers, conspiracy theorist, free speech idealists, whatever you want to call them). It also probably caused him some backlash from the mainstream, which I imagine hurt his career prospects. Therefore, he becomes reliant on appealing to his new following. For status, exposure and income. So he becomes more and more what they want him to be. This may be subconscious, or conscious, or a combination of both. So he's incentivized to go further and further down that path. The more he becomes entrenched in that world view, the more followers he gets, donations, interviews etc or whatever it is he does for an income these days. Same thing has happened to many others.