Illusion in German, just like in English, refers to a deceptive appearance or impression. It's a word that carries a sense of unreality or false hope.
In Pietro Lombardi's song "Warum," he questions, "War es eine Illusion?" (Was it an illusion?). This perfectly captures the feeling of heartbreak and confusion when a relationship that seemed perfect turns out to be something less real or lasting than he believed.
Pietro Lombardi's "Warum" ("Why") is about the confusion that follows a breakup that came out of nowhere. He keeps asking why it fell apart so fast when everything had seemed perfect, and he admits he can't quite let her go.
He describes the small, quiet signs of the aftermath: she won't pick up his calls, he checks her stories just to see she's doing okay, and he wonders out loud if he was ever enough for her.
By the end he tries to convince himself he's moved on and forgotten her, only for her to suddenly turn up at his door, undoing that resolve. The song stays in that unresolved space between wanting answers and wanting her back.