My dad's mom was relieved when her good-for-nothing alcoholic husband died, but on my mom's side it was a lot like you describe. My grandfather was not a big womanizer but my grandmother stopped putting out after she'd had 2 children, so my grandfather got a mistress. His cover was that she was one his customers for picture framing, in fact his best judging by the amount of attention she got. When he died his mistress showed up at his funeral weeping and wailing. Unfortunately I don't remember any of this. I got it all from my mom. To my grandmother it was an indication of what a wonderful guy he was. "Everybody loved him." She died of grief two weeks later, still clueless.
Incidentally, both of them were racists even by 1950s standards. That I do remember.
https://link.medium.com/FcxaY65gTpb