Shared passion for music: They both cherished and found solace in music, a universal language that transcended their individual circumstances.
Sympathy: Feeling misunderstood and isolated Erik may have seen a kindred spirit in Christine, recognizing her ability to understand his internal torment
Ultimately, it was a complex amalgamation of emotions fueled by his unique background combined with her talent that made Chrissti e the central object of the Phantom's desires and affections.