Answer: they needed new territories in the competition for the dominant position in the world. At that time social Darwinism effectively invaded European political thought so there was a faith that certain peoples are superior to others. Example of that can be so-called Scramble for Africa (partition of Africa between 1881 and 1914).
Explanation: Europeans considered themselves superior to Africans, Asians of Latino´s and believed that the dominant role of certain peoples was simply a law of nature. The same logic existed in Europe itself. New colonies could help significantly to the dominant position in the world.
