Why were cartoons so dark in the 2000’s?

I remember my mom showing me what she grew up with in the 80’s and it was cute. I feel like the animators in the 2000’s just wanted kids to have nightmares 😅 my favorites were Invader Zim, Grim Adventured of Billy and Mandy, and Courage the Cowardly Dog. I do recall hearing a rumor that Nick faced a lot of backlash with Invader Zim because of its content. Like in one episode in particular, where Zim stole a bunch of organs from other children, so he can appear more human. Apparently that gave some kids nightmares.