He had an affair because he is an insecure man with low self esteem who felt his ego stroked by a 20 year old nurse who told him how amazing he was because he was a doctor.
She loved him for his doctor title and status because she is of a lower status herself and she thinks it props her status up. You love him for the intelligence that he needed to become a doctor because you are his equal. You know what effort it really takes to get where he got in life and she doesn't. I bet if you pointed this out to him he would concede which love is more real and about him, not just something superficial and self-serving. Trust me on this one. I KNOW.
