PewdiePie is one of those liberals guys that didn't give a fuck before, then did some "joke" that got the left angry and is being pushed to the right ever since. Not that he didn't have any tendency for shitty views before, it's more that he didn't care and will never understand/agree that jokes are harmful or shit like that.
JonTron was one of those cases, but of course he went to more extremes than PDP lol. But before all that the guy was pretty liberal, supported Bernie Sanders during the elections, made jokes about Trump and shit. Now he's Jon "rich blacks commit more crimes than poor whites" Tron.
The thing is, extremes will always push someone to the other side. You're treated as a monster because of something, people don't care about your views on something, of course you'll going to get friendly with people that will accept you and consider you a human being. Even if it's a lie.
I never watched PDP, and only watched a bunch of Jon Tron's videos (before his mental implosion) and it did seem weird the turn he took, even some of the comments/jokes in his reviews.
But then again they say he wasn't shy about dropping the N word on Game Grumps, and i've never watched that.
As someone who's had a family member that went from extreme left, to (not so) extreme right, and back to extreme left, in front of my very eyes, i can say that some people are very easily swayed by their current group of friends and external pressure, and don't really care about the politics themselves all that much, as long as they're in the group.
GAF and Resetera (and 4chan, and The_Donald, etc etc) are proof of it if anything, but that is not to say that anybody should give Jon Tron or PDP a pass, Jon Tron especially went so deep into the eugenics rabbit hole, i'm not sure what he could even say at this point to come out of it, short of providing medical proof of a brain tumor.
PDP i haven't followed, but last time i checked, he had made some edgy jokes and that's it? I can see someone retreating in absurd positions as a knee-jerk reaction to the backlash, it's not unheard of (especially if the backlash is, or is perceived as, overblown and unjust).