Why was the keep built on a high earth mound?

The keep was built on a high earth mound, or motte, primarily for defensive purposes. Elevating the structure provided a strategic advantage by allowing defenders to spot approaching enemies from a distance and making it more difficult for attackers to reach the walls. Additionally, the height of the mound enhanced the visibility and prominence of the keep, reinforcing its status as a stronghold and a symbol of power in the landscape.