How could you have a relationship with a married man?

I can’t understand how a women can knowingly have a relationship or sleep with a married man. Don’t they have a heart or empathy for other people. How could you do something that you know is destroying and breaking the heart of another women who married him. How can they knowingly wreck someones home and life?

Edit - I am completely aware that the husband is way more at fault because he is the one who is personally betraying his wife. But I mainly made this post because I can’t understand how some women do this. I couldn’t imagine ever doing this I would think about the wife and how much pain this would cause her. But I guess I think about other people’s feelings even if I don’t know them I just have standards of things I could not and would not want to ever do. My best friends husband cheated and had a affair with another women they met at the hospital while their son was dying. It practically killed her and she thought this girl was a new friend who was there to support them because she was going through something similar. It broke my heart too watching her go through all the pain of losing her child and husband all at once. I did and I know she did feel anger towards the women ( also the husband). I still wish these women would really take a minute to think about the pain they are causing as well