So why is youtube doing this? It's easy, advertisers are the ones becoming more and more strict and they're the ones in control so youtube has to bend over backwards to please them

Yep

I'm not sure if the world is just becoming more "soft" in general, in many cases this is a good evolution in my opinion, but there's other cases where this mob cancel culture mentality is leading to some absurd power effect where companies literally fear doing something they'd want to do just cause a bunch of random losers who spend all their day on twitter go on these twitter raids

While what you speak of is a horrible thing—I hate this mob culture—I don't think that's what's at play with advertisers becoming more strict, at least not directly. Advertisers just want to appeal to the widest possible audience, and when you want to do that you need to be as "safe" as possible, hence no bad words, no violence. It has nothing to do with beliefs: it is all money driven. How do we make the most possible money, they think. By appealing to everyone and that means making things as bland as possible.