Here's why:

* Impact History: Oberon, like most moons in the outer solar system, has been bombarded by asteroids and other space debris throughout its history. These impacts leave behind craters, which are a common feature on its surface.

* Observational Evidence: Telescopic images and data from spacecraft missions like Voyager 2 have revealed numerous craters on Oberon's surface. Some of these craters are quite large, indicating significant impact events in the moon's past.

It's worth noting that Oberon's surface also shows signs of other geological processes, including:

* Tectonic Activity: There's evidence of faults and canyons, suggesting past tectonic activity.

* Possible Cryovolcanism: Some features on Oberon might be related to cryovolcanism, where ice erupts from the moon's interior.

So, while craters are prominent on Oberon, they are just one part of the complex geological history of this fascinating moon.