I would like to answer your question but need a little more info. Is this supposed to be an essay of a certain length or other requirements? When do you need the answer?
No, it's not a homework assignment. I am just a curious person. My answer can be provided whenever possible. Thank you.
Why would they do this instead of any of the following: Hire a maid or butler to work for them for inside work, hire a gardener to work for them for outside work, do the work themselves, or procrastinate and/or live in a messy house. Any one of these 4 options or a combination of would have been better than kidnapping, abuse, and brutality.
There was lots of outside work to be done, heavy and long--clearing forests, pulling rocks out of fields to plant, planting, harvesting, animal care, etc. they did not have the money to hire all these people, nor did they have the people. Some sects believed that blacks were dark skinned because they were "sub human"--marked by the devil. People over the centuries have committed many acts of abuse and brutality, but greed often wins out.
Is the reason why they were not able to make slaves out of Indians because Indians always stuck together and were not afraid to die since they were Indian braves and fought to the death and because the entire Indian tribe in large numbers would come looking for any one of their own that was lost?