Why did plantation owners begin to import African slaves to work their farms?

One of the main reasons they brought slaves over was because they were very lazy and they wanted others to do the work. The other main reason was because they found out slaves didn't get sick as easily. African Americans are immune to malaria to begin with. Back then malaria was kind of a big thing and if they had people that they did not have to pay and they did not get sick as easily, they found it beneficiary and they used the slaves for that.