I like to think this is a reversal of alone where it was Luigi who got kidnapped and after mario failed Luigi freed himself and swore vengeance on mario for failing him hence "you thought you could just leave me in the darkness all alone" and all the imagery of mario crossed out
My name's angry luigi. And I'm super fucking mad! I don't know what to do. I'll just sit alone and sad. There's nothing in this world that can makes me smile. Honestly it's complicated why im so hostile.