On a more serious note:
A clinic reason its popular,
Scroll back around 9 months, to October. A article was published scaremongering about the death of origional animation and the growth of animation produced just to sell toys, citing the new My Little Pony animation as an example.
So People went to watch, hoping to get some amusement from its cheesy badness, except it wasn't-Well it's sugary as hell but Importantly it knows it is and takes advantage of it. So when the classic "Bookish Social Recluse" character meats up the "Hyper Genki Girl" character, the first thing that happens-She walks over to the drinks table with a pained expression on her face and pours herself a drink.
Its was this kind of self awareness that made all that made it all bearable(Opening notes of a song start playing "Tell me she's not"(First line of song) "*sigh* "She is".
Its not the best piece of animation ever but its defiantly the best piece of animation ever Compared to what was expected of it.
Personally I enjoy it as I see a show that actually teaches morals to live by "Sometimes your friends are jerks, don't let them get away with it-It won't end well", and the series of a whole has one of the best of all "Don't define yourself by what you (think you)can do, define your self by what you enjoy doing" All without ramming it down your throat.