First off, it's a funny show. It is an excellent comedy disguised as a cartoon for girls. If you titled the show "Ponyville" and showed it at 8pm on ABC, it would get good ratings. Nobody would conclude "oh, this is a girl's cartoon." In many ways, it's a wacky comedy, of the kind that hasn't been seen since the 60's.
Next, I think that male media is currently so messed up that most males don't identify with it any more. Given a show with character that they can identify with, males naturally respond by identifying them, even if the characters are female pastel ponies.
Supposedly, males in their 20's are a big demographic of the show. Not surprisingly, that is the post college age where you are hopping job-to-job and place-to-place. At that age, you have not adjusted away from your school age friendships yet, nor have many moved to having families yet. There's an empty place in your heart for all that stupid friends stuff that you used to do. Many folks long for those times when friends were just across the hall or a few blocks away. That FEELING of having friends again, even for a little big, is really good.
I think that there's a cynicism exhaustion. I think that many people want off the cynicism treadmill, but you can't get off it because that's the only attitude offered via the media.
So the lesson here, I think, is that media is underserving everybody, and if you produce something worthwhile, you'll have very little competition.