Narcissism works because its victims don’t see it.
Victims don’t see it because they are children being raised by narcissistic parent(s) or very commonly adults who were raised by narcissists. There is even a term for the latter: ACoN, Adult Children of Narcissists.
Other kinds of people also fall for narcissists, but having been raised by narcissistic parent(s) is probably the most common.
Narcissists often appear normal to others due to narcissism being a fairly common disorder and also due to the narcissist’s deep-seated need to appear normal to others. They are experts at “impression management.” That’s a big part of what narcissism is.
For many ACoNs, narcissistic traits look perfectly normal because that is what they experienced at home. Narcissistic smiles, glares, malice, selfishness, ostracism, false concern, abuse, and more all seem normal because they were imprinted on the primary instincts of the child to need and trust their parents and siblings.
In truth, entire cultures can be narcissistic, abusive, hierarchical. To break these habits in interpersonal relationships, you have to do FIML practice or something very similar.