European colonists were claiming the land hoping to outdo their neighboring European competitors. In the time where colonizing a country is a regular, most European countries were scrambling to claim a stake in African land for its resources and raw materials.
I believe the answer is: European colonists were claiming land hoping to outdo their neighboring European competitors.
The African continent was known among European colonists for their rich natural resources ( especially metals) and their slave markets. Because of this, the european nations involved in a race to extract the African land for its resources in order to obtain the most economic benefit over another.