Honestly, I don’t. Or perhaps they are hesitant to mention it or don’t recognize the particular brand of abuse they were subjected to. It took me years to accept my mother was the textbook definition of a narcissist. She hid it well to those outside of our home. She was proud to the detriment of her children; she was negligent to the point of abject poverty; she regularly gaslit or lied; she was manipulative and strategic; she alienated each of her children from one another; she applied favoritism and double-standards (treating her daughters like garbage and her sons like kings), etc... There are hundreds of horrible little scenarios and stories I could tell, but it isn’t worth drudging up. Sufficit to say, she is a narcissist and it was difficult to come to terms with seeing as her facade was warm and comforting. But her personality and motivations were/are insidious.
In terms of finding others who have similar experiences, I found a group I connected with where many of the women there talk about the abuse they suffered or are still suffering (specifically at the hands of their narcissistic mothers and the flying monkeys who did their abusive bidding).