Many of these so-called ponies believe they were the first to discover the land that is now known as Equestria. They were wrong, of course, those silly Humans, Dwarves, and the pitiful vomit-inducing Elves littered the landscape first while living their simple, boring lives. The ponies and the other races simply moved here over time from some other land. If they were still here, the various original races meeting the ponies would have made for a bit of a chaotic first contact. It's too bad that didn't happen, oh I could have enjoyed watching that with a nice bowl of salamander eyeballs.
But, well, one or one-hundred powerful wizards attempting magic beyond their capabilities on magical artifacts beyond their comprehension tend to make things go explodey. In a single snap of my claws the entire human race, and all of the other "intelligent" races as well, were simply gone. The landscape even more magically scarred than when the Tower Heart of the old Dark Tower went kaboom. We minions fled back to the Netherworld from whence we came and waited for the land to heal, and hopefully for some other race capable of thought to come knocking at its gates.
We waited a long time for that and now we should really get around to finding a new Master. Giblet seems to have found something promising while digging around the cave of a local dragon (the dragons seem to have gotten smarter too), so I'll have to go give that a look-see and pray to Darkness nothing weird comes out of it.
But as they say... Evil always finds a way.