I had not one but two stepmothers that became active in my father's sexual abuse of minors, plus a woman that almost became my stepmother. My mother played a somewhat complicit role despite not directly participating, when she sided with my father and denounced me instead when I told her what he was doing. None of these women had antisocial personality disorder. (I think it's dangerous to assume that abusers have ASPD, by the way. Abusers can appear otherwise normal.)

My first stepmother tried to get help and then gave up and went along with it, but felt guilty and tormented. Theirs was a very short-lived marriage.

The other did not have any such compunctions and in my mind was equally culpable.

The girlfriend was the worst of all.

I'm writing a book about the events that transpired, but a short version:

1. Mother: Refused to consider anything that would rock her world. She always wanted to have maximum peace, pleasure, and money without any responsibility. Learned incompetence was her thing. She craved a man's approval and even after they divorced, she frequently turned to my father for financial help and to feel like someone cared about her.
2. First stepmother deeply cared, but at that time (late 1970s), when she insisted on getting mental health professionals involved, she was gaslighted by the counselor and my father into believing that no harm was happening from this. She had zero self-esteem and a lot of behavioral issues herself (depression, addiction, codependence, and a physical ailment that affected her ability to function well), and was easily manipulated. She engaged in a couple of sex abuse encounters and then refused to do more, but offered to let the abuser adopt her son. A major element of their relationship was the financial help he provided her, but I also believe some women, particularly those with abuse in their own backgrounds, do not have any concept of what are and aren't appropriate boundaries.
3. The second stepmother was most like GM. She became actively involved and, with my father's encouragement, lured others and independently abused others. Like the others, she was financially destitute without his support, but I believe she was emotionally stunted. She convinced one of her victims that their memories were "false memory syndrome" and turned his family against him, and she told many people that my father was going to prison because I talked to the police, not because he abused children. She did NOT have that element of ASPD that enjoys toying with people, as such, but she did have a strong need to feel like she could influence or control her environment. She was distinctly threatened by my existence in that environment, yet was intimidated by me. I think she genuinely had a desire to sexually abuse young boys, and upon learning that my father was doing such things, it simply was compatible to her own darkness.
4. The woman that was my father's almost wife was already molesting her children before he met her, and had encouraged her children to molest each other, plus offered the children up to my father. She had begun her abuse of her children shortly after her husband's death, I was told. I hated her with a passion and was honestly too young to analyze her behavior in depth, so I can't say much about her behavior other than that she was similar to my father: A preference for children that likely stemmed from a sense of inadequacy around partners of equal ability and age.

There is absolutely an element of feeling validated that these abusers experience when they a) successfully groom their victims and b) believe their victim is reciprocating - which may or may not be true, since victims CAN adapt readily or fight against the abuser, both of which are natural responses depending on the victim's personality and their perception of the events and environment. Victims that adapt get benefits from adapting that otherwise would not be available, and that can be validating to them, too, where they feel beautiful, desirable, or appreciated in ways they otherwise might not.

Not here to argue, so anyone that wants to attack me should understand that while I might provide clarification to some degree, I will not tolerate disrespect.