The difference is that the guy who mugged your mom was not a celebrity. The focus was on her, as a victim; no one, except possibly his family and closest friends, was conditioned to believe in his innocence and accuse her of trying to bring him down.
This story began with Bryant. “Kobe Bryant accused of rape by [somebody].” Not “Jane Doe raped by [somebody].” I understand, though I do not share, the inclination some have to think of Bryant as a victim in this case.
Lots of guys were perfectly certain they would get away with it, too, knowing that women seldom report, and that the conviction rate is minimal. ("Men on Rape", Tim Beneke.) It's not out of the realm of possibility that the guy just doesn't think he's a rapist. If he just believes his press, he's going to feel entitled to all sorts of things.