I don't know. All I can think is that a parent might make excuses for such a child and seek to protect them from being found out, or the child learns to hide the signs that they understand cause suspicion in others, and so the adults just have a suspicion that the child "isn't right" but they don't have proof, and maybe they want to blind themselves to it and hope the child will grow out of it?
It's not something I've researched, but I remember reading something about an empathy gene, and that most people would have either one or two copies of it, but those without any copies of it might be more likely to have this personality type? But there has to be more than that to it? I think nurture can play a role, yet I also think sometimes psychopaths are born to the nicest mothers (usually it seems to be the mother in the household and the father is either absent or always working or something? At least in my mind it's that way.) and that the mother simply can't cope with the child. Maybe sometimes the absence of the father part of it? Not in the sense that a child needs the father figure (though I do think that having healthy role models in parents is a good thing I also think that a single parent can provide the role model where that's the only or preferable option) but in the sense that maybe there could be a father to son genetic component and the father isn't good at forming relationships or tends to form abusive relationships so he either abandons the family (lack of empathy with their needs) or the mother leaves with the children? Or maybe the father ends up in prison and that causes the separation?
But I don't really know enough about it to have any more than these thoughts in my mind, I can't point to research to confirm or deny what I'm suggesting.