Yeah, I'm gonna have to agree with all the pewdiepie answers. Pewdiepie's popularity is a fucking enigma to me, because there was a point in time where damn near everyone who knew who pewdiepie was hated him. He was very often criticized for his loud and crass sense of humor, his fanbase and their annoying groanworthy references, and the honestly kind of cynical way he ran his channel at the time.
You know what's changed between now and then?
His channel isn't a primarily gaming-focused channel anymore.
He's now the largest and most celebrated Youtuber on the platform.
That's basically it. I don't think his popularity is just confusing, I honestly think it's insidious.
Because here's the thing, his sense of humor now is loud and offensive, it always is and always has been, but his actions lend credence to the notion that it's more than just a sense of humor. He's landed in hot water more than a worrying amount of times over racially insensitive jokes and remarks, has notably promoted and hosted far right content creators on his channel, and proceeded to cast doubt on any media outlet who reported on any of this. This is what I find insidious about his character and his popularity. Nobody ever holds him responsible and he doesn't hold himself responsible. The closest thing you can expect is he puts out a scripted apology video before going right back to what he was doing before and inevitably landing in hot water again. The largest creators on the platform promote him unquestioningly and always jump to his defense when his newest controversy comes up, and the few times someone does criticize him or hold him accountable they usually get bullied for doing so. He has probably one of the most toxic fanbases around. You can argue day and night over whether or not pewdiepie is actually racist, far-right, or whatever the case may be, but even if completely by coincidence, he is very popular with racists and the far-right, and he hasn't made any genuine gesture to denounce them.