If you look at the establishing shot of Jedha from above, the layout of it is this giant, circular rock formation around where Jedha is–the idea was that there was a meteor impact that hit Jedha and it came at such a force that it was what created the Kyber Crystals at the center of that crate of impact.
We tried to tell that story in the establishing shot, you see the circular formation and at the heart of it is Jedha city.
So Jedha is like this very unique place in the galaxy in that it’s got a very high density of Kyber Crystals, which is what the Jedi need for lightsabers.
So it became this holy city as a result of that meteor impact.