Why did the number of tenant families increase steadily post Civil War?

After the Civil War, during the Reconstruction era, most of the freedmen in the South went back to work in the cotton fields as a way of sustenance. However, since they were already free, the Radical Republicans in Congress thought of a way to make former slaves free-holding farmers. This resulted in the vast majority of freedmen becoming tenant farmers. Thus, tenancy and sharecropping became fundamental in the southern Reconstruction process.