The dark forest hypothesis sort of existed before Liu Cixin.
Berserker event is effectively an implementation detail of one of possible events in the Dark Forest.
Like Wikipedia says, Dark Forest is for people who are limited in tech and resources. Or have a weird sense of ethics, but ask Robin Hanson how long he thinks that would last.
It's based on another article that claims that people mostly interacting in their own social bubble, fueled by algorithms which mostly isolate people further, is akin to making the Internet a dark forest.