Very interesting! I never knew about that Youtube change in 2012, but it does explain some things I've been noticing.
PewDiePie's popularity got me curious at one point, so I decided try and understand why by occasionally watching a bit of his stuff. While I had never really enjoyed the videos where he played horror games (because I found his loud screaming after jumpscares unpleasant - especially when he was using a cheap mic), some of his Happy Wheels compilations actually got genuinely laughs out of me several times for his tomfoolery. And when he plays a recently released interesting looking or AAA game or just a game that I enjoyed (like Dark Souls for example), I was actually entertained watching him (or at least I didn't really mind his commentary while taking in the game footage). Also, he actually edits out the boring bits thereby saving me time, as opposed to some of the other Let's Players I'd been used.
It's a hit-and-miss for me, but since he produces so much content, there are still bound to be relatively many hits (at least for me). ...Or something like that. And when he gets to play games before release, his videos are also a nice method to get acquainted with a new game without spending money. And I guess PewDiePie genuinely has fun while on camera and you can tell, and it's kinda contagious sometimes.