It's terrifying to become intimate with someone like this as you slowly realize there's a glitch and part of their soul is missing. And they think they are always right, and will never understand what they're missing in their prefrontal cortex.
But oddly enough their mental defect serves them as a strength & an intimidation factor as they go about life intermixed with neurotypical people, they plow through life unbothered, they win at everything as they remorselessly use & manipulate & plow through everyone in their path.
I wish in some dystopian(?) utopian(?) parallel universe these people would be identified then given a one-way space flight to a different planet where they all would live amongst their own kind. What do you think an entire planet populated ONLY with narcissists, sociopaths, & psychopaths would be like?
Let them all use & manipulate & destroy each other their entire lives while we innocent guileless fairer folks can have our peace restored.
you are assuming they had knowledge of those red flags or warnings.
many people don't. most only learn about them through the experience.
it is easy to ID such people once you have had first hand experience with them, but nearly impossible if you haven't. and some folks never learn to see the red flags.