I think there's the issue of his channel blowing up in terms of subscribers and views leading to him making quite a bit of money, especially leaning into the anti-vaxxer or "sceptical people just asking questions" kind of narrative. At the same time, I think he was always kind of on the "alternative" side of the narrative. Not in terms of being a Covid-denier or a complete anti-vaxxer (I think he's fully vaccinated with a booster), but his whole "Vitamin D protects against Covid"-narrative was a bit suspect from the start.
If I'm honest, after watching his videos for a few weeks after the pandemic had started I was fully expecting him to come out with his own line of Vitamin D supplement Alex-Jones-style because of the way he was going on about it. Not saying that getting all the necessary vitamins and whatever else your body needs to be healthy is bad advice, but he was going way over the top with it. Haven't really followed him after that, so can't really say where it all went sideways, but I would imagine it's a bit of everything, i.e. creating controversy to get subscribers and views, keeping his followers happy (which have gone from mostly being people thankful for him explaining what was going on in the world to being the anti-vax, covid-denier crowd), being open to the whole "being sceptical" narrative himself and getting involved with the wrong people on YouTube. It's good to see that there are loads of people debunking his (and other people's) bollocks out there. It's kind of sad that a lot of them have only small subscriber counts...