Do we really know why anything is popular?

Whenever an anime or manga is super popular, be it with “casual” fans or super hardcore 4channers or die-hard bloggers or anywhere in between, someone eventually decides to ask, “Why is this popular?” The question can be interpreted positively, encouraging people to express why they like that work so much. It can also be interpreted negatively, giving way to sweeping generalizations that categorize a work’s fans in a particularly unattractive light.

As a quick demonstration: Why is Baka to Test to Shoukanjuu so popular?

We can posit why Gundam isn’t popular “here,” or why Captain Tsubasa is popular “there,” but after a while I just have to wonder how often we’re putting the cart before the horse, completely blinded by hindsight and trying to draw conclusions from something most people might have trouble expressing in the first place, even if you asked every Naruto fan why they like Naruto so much. And in a way, when we accumulate more knowledge and experience in anime, we paradoxically move both closer and further away from the truth.

Not saying I don’t enjoy the speculation, nor am I telling people to stop, but popularity (or lack thereof) can be such a difficult entity to grasp and manipulate that I’m sure we’re all wrong more often than not.

Also, I know this doesn’t just apply to anime or manga or even fiction. Asking why stuff is successfully popular is applicable to just about any topic where  group enjoys or uses something.

No, really, why is  Baka Test so popular? I liked it well enough because of the way it embraced the otaku/moe/anime humor and really ran it to some logical extremes, but why is it considered the #1 light novel series of 2009?