Why did blanches marriage fail?

Blanche's marriage failed primarily due to the emotional and psychological strain stemming from her husband's suicide, which resulted from her discovery of his homosexuality. This trauma left her struggling with guilt, insecurity, and a deep sense of loss, ultimately leading to her inability to maintain healthy relationships. Additionally, her fragile mental state and reliance on illusions further contributed to her downfall, making it difficult for her to cope with reality and form lasting connections.