CanonRumors is a good site about... You guessed it, rumors about upcoming Canon gear. It's actually a great site, the original afaict, read by a lot of working pros and amateurs alike. The posts by CanonRumors Guy are balanced and vetted (as well as he can for rumors, anyway), and the discussion boards are great if you're a canon nerd. It's really hard to see the guy have one really shitty day on Twitter and as a result have his site basically go up in flames. I don't know GeralUndone from a hole in the wall, but there are more than enough YouTube reviewers, while CR played a very important part in the Canon news ecosystem. As others have said here, plenty of YouTubers source their info from sites like CR.
I'm guessing the wall of ads in his last post is because CR Guy is bitter about how YTers are paid relative to his site, but he doesn't realize how many appreciate his work.