"Because of what Faust is. I know she models herself as the pinnacle of Harmony, but that isn't the truth, not entirely. Where Discord is the spirit of Chaos, Faust is the spirit of Order. He and Faust are natural enemies, or so they think. Even after Faust realised that they could create harmony by working together, they were still massively at odds, which is why the Golden Tree failed. Faust tried to create it from the singular standpoint of order, but order alone is not harmony. She introduced chaos to the Tree of Harmony, striking a true balance, which is why it succeeded."