: The Europeans who did most of the transportation of slaves from Africa viewed then as godless heathens and therefore a non-human in a way which gave them justification to exploit them for labor while "trying" to teach them about god.
2: It was a logistical god send because of the Colombian Exchange and advancement of sailing technology that allowed for Africa to become the in-between from Europe to South America which allowed for the selling of sugar/Rum in Africa while buying slaves to sell in North and South America.
3: They were a fairly easy "resource" to "harvest" because many warrior tribes inhabited Africa and would capture and sell their competing neighbors to the slave traders in exchange for rum and weapons/supplies.
Explanation:
They had weapons, their societies were separated, which made it easier for them to take over
