Slavery has existed for all of human history. It’s only been in the last 150 years page scores of humans have realized that it’s wrong. There are still plenty of countries and societies where people are enslaved and treated like chattel.
We see it as evil because we are enlightened enough to see that humans are essentially all the same, but the idea that humans are not born equal can be found throughout history in all societies. Equality is a rather new idea.
Some slaves were treated better than others. House slaves (which were often the children of the slave master and the women they raped) were often treated better then field slaves.
Some slave masters were kinder to their slaves. Other slave masters were brutal and harsh. The conditions of slavery gradually grew worse prior to the Civil War because of the increasing amount of laws that limited the rights of slaves and Free Blacks. This was done in order to limit the chances of slave uprisings, a constant fear that was held in the South.
The one thing that makes me (a bona fide senior citizen, allegedly) feel “old” is that most people think of the Civil War and Reconstruction as history, as oppsed to “things that have been in living memory of members of your family who were your own contemoraries”. My grandmother, who I knew well, was born in 1898. She had lucid memories from before WWI. She had known people whose parents had either been slave owners or slaves themselves. Elderly Civil War veterans were extant if not common. The war is, the way I think of it, “recent history” because of that generational connection, in a sense that the Colonial period is not. I realize that’s a funny way of looking at the world, it’s how I see it.