Why do you think african slaves brought to the americas to replace native americans and indenctured servants

Likely because native americans existed in very few numbers - with a steady decreasing population and indentured servants weren't owned like property. It was sort of like working a job but still having a certain amount of livable freedom. Once African American slaves were in America they steadily increased, which means they could work more and create a system of economy. Even if it suffered from immorality.