When someone puffs himself up so massively, we naturally want to poke a hole in that hot air balloon in order to deflate him. When he lauds himself as the smartest, shrewdest, wealthiest, and most successful person in the world, of course we'd like to cut him down to size. Satirical humor allows us to do just that, even if we've never met the person.
It's easy to poke fun when you are an uninvolved spectator watching from a distance, the way we are with Trump's antics.
But naricissism is a very real disorder that, when encountered up close, such as in the workplace, isn't so funny. It's much harder to laugh at a toxic colleague who poisons the workplace than when you're watching someone on TV from your couch.
Narcissism occurs along a spectrum of possible expressions, from healthy self-esteem on one end to narcissistic personality disorder on the other. On the pathological side, narcissists have a grandiose sense of self-importance and little or no ability to empathize with the feelings of others.