Narcissists truly are experts at reading people. Many people have come to me and hold me how great their narcissist is at duping people, getting others to do and believe things, and how afraid they are that nobody will believe their side of the story- the truth. Narcissists spend every waking breath of their lives trying to control their environments so that narcissistic supply is readily available and easily accessible. Inclusive of this is studying the people around them so that they can quickly identify and ensure that someone will be a viable source of supply for them. Remember that the narcissist doesn’t attach themselves to people because they have little value, they attach themselves to others because of how much value they have.
I once read an article written by someone who identified as a narcissist (I know, shocking) and explained how she developed expertise at reading people. She told the story of her childhood and explained that she was raised by parents who were less than nurturing, probably abusive and likely narcissists themselves. As a child, she had to learn how to read her parents so that she could know when to ask for something, when to appear or when to disappear. Most narcissists become narcissists because of his or her childhood. Many narcissists might have to learn how to read people for what seems like their own survival- starting at an early age; thus, they become masters at it when they enter adulthood.
Although narcissists become experts at reading people so that they can survive off of their oxygen- narcissistic supply- there is a way to defend yourself against them. The key in doing this will be to continue researching and learning about narcissism, creating super strong boundaries along with a super strong strategy so that you can end up in a position that you’re happy and comfortable with.