I don't pay attention to him much anymore since he mostly stopped doing his regular show as far as I can tell for awhile now. Watched some of his podcast stuff and flea market stuff awhile back, but there were times where he didn't seem overly knowledgeable about the topics unless it's very retro related and his podcast is very off the cuff, so it's gonna usually lead to regular hot takes on things. That said, he most likely doesn't deserve the shit he's getting, especially from a nasty mob like what PewDiePie is gonna be sending his way, but I'd probably not agree with Pat also, just going off the premise put out as I'm not gonna watch the video.
The uproar might be overblown, it usually is (Battlefield V is a good example of how fucked up it gets), but looking at the information, this was Blizzard just completely doing everything they could wrong. This wasn't the audience that was waiting for some weak looking mobile game, the fans who paid to watch it at home didn't want that, this wasn't the game you ended the keynote on, they had both teased and downplayed Diablo being at the show, it only got worse afterwards when it was noticed that the developer for the game had previously made a mobile Diablo knockoff and was just re-skinning it and adding some extra stuff to make a Diablo game. This was not something that serious fans wanted at all and this was reflected in the feedback.
There's not a single thing wrong with them making a mobile Diablo game, but as EA showed earlier this year with Command & Conquer: Rivals, not keeping your fanbase in mind with these things can go real bad.