One thing to add to what others have said:

After having done these three or four very questionable things, people realized that YouTube's algorithm was essentially sending Pewdiepie's viewers down a radicalization pipeline. The algorithm would start recommending alt-right content to people who had watched Pewdiepie videos.

He himself still at that point made fun of the journalists who reported on this, essentially showing the stance of "I am not responsible for what my viewers do" and "I am not a Nazi and I am not radicalizing anyone".

In response to the fiverr video in 2017 he was dropped from his partner network and his Youtube Red show was cancelled midway into production. Additionally in what was called "adpocalypse", advertisers forced Google to disable ads from being shown on controversial videos.

And then in March 2019 a Nazi terrorist livestreamed himself shooting 50 people in two mosques in New Zealand. Before starting to shoot, the terrorist screamed "Subscribe to Pewdiepie!" This was the point where he finally seemed to wake up to the fact that some of his viewers actually were far-right extremists. And he stopped doing any edgy stuff that could be interpreted as being pro-Nazi.

In the past, he was a gaming streamer. During many of his streams, his actions and words strongly suggested that he was racist and/or a Nazi. At least once, he was called out for using the n-word (with the hard r). He has never expressed any remorse.

Because of that, many people consider him to be the gateway of the alt-right pipeline. Essentially, children are attracted to his channel for the gaming content, and over time, they are influenced by his behavior to be increasingly accepting of racist and/or alt-right content (after which the YouTube algorithm will then feed them increasingly extremist content)

Since at least several years ago, he retired from his channel, started a family, and moved to Japan (not necessarily in that order). It's entirely unclear if he's changed his mind about any of his previous behaviors, and in the absence of any indicators of change, many people take the stance that he probably still is a racist/Nazi

Here's a couple of deep analysis on pewdiepie and the alt-right

The pewdiepipeline, how racist humor lead to vialonce: https://youtube.com/watch?v=pnmRYRRDbuw

The Alt-right playbook: How to radicalize a normie: https://youtube.com/watch?v=P55t6eryY3g

And additional points that no one had mentioned is that pdp, did a couple of videos, meme reviews, with people like Ben Shapiro and recommend books from Jordan Peterson, sending his million of impressionable young audience directly into misogynist, racist and homophonic content creators.

I know the name PewDiePie, but I have no idea why he's so famous or why he was one of the biggest streamers in the world.

I'm so OOL that I don't know who this pewdiepie is, sorry!

Is PewDiePie one of those ponies? Or a Brony?