3 things I think are responsible for the decline:

1) Generative AI is cutting into views across the World Wide Web. No one wants to read or search an article for an answer when AI will provide a concise answer to a specific question.

2) As Adam122 says, people are looking at videos more than ever. And Google is serving up YT videos before SEO links for the obvious reason that Google owns YT. I know I prefer video reviews of premium cabins even to Ben's photo dumps.

3) Niche discipline. As others have said, he is muddying up his niche. And niche is key to optimization and monetization.

JMHO as a marketer.