My grandfather once did the same, with exactly the same results. Its hardly ever worth bothering to intervene in a domestic violence situation. Women who tolerate being beaten by their husbands are usually lost souls who cannot be saved from their own folly and psychological dependence on the thugs they are stuck to. If they aren’t willing to save themselves, why should others bother?
OH don’t get me wrong, I’d get involved again, but I’d just take a 2x4 or whatever I could find to the creeps head and be done with it on the first blow, yes no problem with a sucker punch or groin kick or whatnot.. not going to sit there and watch them beat a woman, she can then nurse him back to health if she chooses, but I will not put myself in a situation where I do not recognize that the woman may be a threat as well.