As Generative AI becomes a key source of social and emotional companionship, it reshapes parasocial relationships (PSR) in the digital age. This study explores the mechanisms behind these one-sided emotional bonds using a hybrid PLS-ANN-NCA approach, integrating sufficiency and necessity logic with deep learning. Results reveal emotional validation as both a sufficient and necessary condition for PSR, with 100% relative importance. Adaptability and anthropomorphism are critical enablers of emotional validation, while expertise is sufficient but not essential. The findings highlight the evolving dynamics of PSR: security and adaptability are vital early on, while anthropomorphism and expertise gain importance at advanced stages. This research offers a causal understanding of PSR formation with GenAI chatbots and provides practical guidelines for designing emotionally intelligent, adaptive, and user-centered AI across mental health, education, and customer service domains.