Answer: Because of mutual rivalry.
Step-by-step explanation:
Europeans colonized almost the entire world. It was a competition among European countries in prestige and the establishment of world domination. Nationalism is a factor that certainly promoted colonization, especially during the XIX. and the twentieth century. The Europeans thus warmed to gain more than their competitors, and gain as much wealth as possible. Such a policy was pursued from the discovery of America until the end of World War II.