It's a mechanism to rant online about your life without the risk of someone calling you on your bullshit. I'm not saying that all of the stories on there are bullshit, I'm just saying that it's (ironically) primarily a label that comes out to describe someone when you are looking to find a narrative that protects your own ego -- because you've experienced trauma and you are looking for a mechanism to not put an ounce of blame on yourself.
Are there narcissists in society? Sure. Is a large percentage of the population narcissistic? No.
When someone "collapses" in the way that the article indicates and/or slights you, does that probably make them a narcissist? Absolutely not.
Calling someone a narcissist lets you freely claim that the other side is incapable of sincere emotion and lets you get away with believing whatever the hell you want. It's popular because sometimes you need to do that to move on. But it's not a healthy way to look at the world.
/rant