Several reasons actually. The most important one was its location. Thanks to it it enabeled the trade with African, European and Asian countries. Another thing is that it also was a good place to start a war on other countries.
I would say that one assumption is the superiority of Europeans over Africans: their belief that somehow they had the right to enslave other people.
This could be connected to their racism (they thought the same of native Americans and there was a discussion whether native Americans have souls) or religious feeling of superiority ("pagans are not the same as Christians"...)
I'm not sure what you're talking about here, but if you are talking about driving then it is
D. Recommended