This post by Sylvette above may not be written in the classiest fashion, but it reads like the gospel truth.
It's what I thought when I first read this by hthe original poster - no woman wants to think her man is a jellyfish. Had this man showed more character, she probably would not have slept around in the first place.
Some women with mamby-pamby husbands will get a lover, subconsciously desiring for the husband to find out and actually DO something about it. When the husband doesn't do anything, the wife will further sink in disappointment, and perhaps the next time she sleeps around she is really looking for what she's missing. This may sound like over generalization, but I guarantee you it's how it works 98% of the time.