TotallyNotNyx

So I've been thinking.

When Starlight messed with time, one future Equestria was one where everything was gone.

For an entire civilisation to be destroyed and disappear without leaving a trace in 20 years, something really major would have happened. But what could have done it?

Even if any of the villains had not been defeated, you would still be able to see the ruins of Equestria, or ruins or remains of any kind. But there was nothing there (it;s been a while since I watched the episode so correct me here).

So what could have caused such a future to happen?