[spoiler][youtube]ggXmKPMaHMo&autoplay=1[/youtube][/spoiler]
*Switches off sarcasm mode*
But yeah, it is not that bad a show IMO. I do not watch cartoons generally although one or two great ones are still running. My Little Pony was not popular before Friendship Is Magic started airing, and there are several reasons for that.
Basically while kids used to collect and buy MLP toys (mostly girls, mind you), Friendship is magic was made and aired on Hasbro's very own TV channel, in a bid to try and get MLP popular again so that kids would buy their new line of merchandise that they could release with it.
Now, the reason why people like the show is that, for one it is nostalgic. And two, the people involved in it were involved in cartoons that, back in the day, were perfectly good. For example some of the Friendship Is Magic crew had worked on The PowerPuff Girls and so a few people just generally thought it was pretty good, especially for something that was supposed to just be a marketing tactic. And when that happens, word of mouth spreads and before you know it, you have a huge group of followers =P.
The reason it became a huge internet cult, or pathetic meme if you will (or if you will not, it is still true), is because some people on 4chan were talking about it, and new rules were introduced. Wherein, people would post pony stuff in random threads and stuff, so rules such as "MLP stuff is only to be discussed in specific MLP threads" were introduced, and this is where "Mods are asleep, post ponies" comes from.
Since then it got way more popular over a short time, and now has a ton of dubs and meme related pictures all over the place. Which also generates more interest and popularity (curiosity if you will).
TL-DR, it is just a new show that happened to become popular, like any other before it.