I've known both men and women to do what you have stated here, so it's not just women who do it to men.
I did it and I found out what I had suspected for months. So yes maybe I should have just walked away but I got tired of the lies, the there "is noone but you baby" so when I had proof and confronted him with it, he still tried to lie at first. Then he came clean. So I had not done it he would have continued doing what he was doing and getting away with it. Am I proud I had to go that route, no I am not. I did it and am glad I did, now he isn't making me look a fool anymore. So as for the trust issue, obviously I didn't trust him as much as he or I would have liked but that is because of the situation. And he had told so many little lies trying to cover his tracks that it became obvious what he was doing.
Would I do it again, no. And the reason I would not is because it hurt so much. In the future if I feel something is out of oridnary I'll just walk instead of subjecting myself to more pain.