Women do not prefer
assholes, as they are rather hard to get along with. But remember women are people, and some women do seem to prefer assholes. For many the cause is in their upbringing.
It has been pretty well documented that women whose parents had an abusive relationship often choose abusers themselves. Some of that is due to simple modeling. People learn most about how to live by observing those around them, particularly those who are close to them. Nobody is closer to a child than his or her parents. If Dad beats mom, well that's what men do. Violence becomes a part of love. Intellectually, of course, women know better. But sexual attraction is deep seated compulsion whose components are often irrational. Violence is normal so it's no big deal.
Another issue is self hatred, or low self-esteem if you prefer. The first woman I ever really loved chased an endless supply of men who used her. The issue wasn't that she really liked them, it was that she hated herself. Many people who have been abused don't really think themselves worthy of anyone good. They distrust love because people they love have betrayed them. They seek the users and abusers who represent their norm.
In both cases, the problem is that they really don't believe there is anybody good out there for them. Of course guys never feel that way.
And if you believe that I have a killer deal on some ocean front property . . . .
As a former 'nice guy' who never had a girlfriend, being nice is no excuse for lack of a personality. Women want to know that there's something in there. You are a person, express yourself! I know from personal experience that's hard when you don't believe in yourself, and you fear losing someone you want. But do it anyway. I started getting dates, and more, when I started developing enough confidence to let my personality out. No, that doesn't mean I get any women I want. Not even rock stars manage that. But I have enjoyed the company of some really special ladies. Sooner or later, one will decide to keep me.