Sometime ago, I was in a short relationship with a chio married woman. We connect emotionally and physically pretty well. From the start, I never inquired about her other half. I respected her privacy. One day, she asked me why I ain't curious that she was "straying" with me. I said I did not wish to know, but if it made her feel better, she was welcomed to divulge to me.
She told me that she had lost interest in her hubbie. "Monotonous" was the word she used. She added that he didn't "cherish" her like I do, cook for her, "asking the right questions about her life and career", and "refraining from sex" and so on. Emotionally, she was already disconnected with him as the latter didn't make an effort to sustain the relationship.
Is she to be blamed for "straying"? Up to this day, I wonder. There's probably no right or wrong answer, I reckon.