Mongolizarme is a highly unusual and striking word, derived from "mongol" (referring to Down syndrome, though now considered offensive in that context). In this song, it's used metaphorically and provocatively to mean to make oneself foolish or to become a simpleton.
The artist sings, "Estoy decidido a mongolizarme" (I'm determined to make myself foolish), expressing a cynical resignation to conform to societal expectations, even if it means sacrificing his intelligence or authenticity. This word is memorable precisely because of its controversial nature and its powerful, albeit dark, commentary on societal pressures.
Have you ever felt so fed up with the world that you just want to give up and stop caring? That's exactly what Ilegales is singing about in "He Decidido Comportarme" [I've Decided to Behave]. The singer is making a sarcastic declaration that he's going to start acting