You have to consider: The internet is rather "new". ;)
In "the past" most people on the internet were either total nerds or teenagers and young tweens. "Naughty content" was not always welcome on NG and teenagers tend to be a rowdy crowd, so it was a lot of violence.
Plus: 'A sea of blood' is easier added to a video than a deep and intricate story. ;)
RosieUV
that's just how the internet and society as a whole has evolved, not just newgrounds.