Because Social Darwinism is a mash between "Survival of the Fittest" and socialogy, races and political groups/parties fought to be at the top. It's natural for large groups in population to think they are better than the rest and given the example of Hitler, Benito Mussolini, etc., it's not hard to see who Europeans think they are. The first option is most likely correct.
Europeans believed they were a more evolved race who deserved to take over others.
Explanation:
Social Darwinism (proposed by H Spencher) was an ideology used to justify imperialism. Until our days, the core idea behind Social Darwinism is that the strongest and fittest survive. Therefore the rest is seen as unfit. Supporters of imperialism believe that the places that were colonized weren't as fit or as a developed as the imperial country was. The idea of bringing "civilization" was then the justification.
The whole justification was the product of late nineteenth-century economic and political expansion. As European, upper classes sought to extend its economic and political power, it used allegedly scientific explanations to justify the huge gap between rich and poor.
The arguments extended to think that the imperial poweres were naturally superior, and that their control over other nations was in correspondence to the interest of human evolution.
