Did it improve? Yes. Did it improve more than the general improvement through advances in technology, medicine etc.? That is at least questionable.
If we look further at unethical experiments done on primarily black communities or prison inmates, again primarily black, such as testing biological warfare agents and pharmaceutics on them, regular lynching and other acts of deadly violence, the whole forced labour in the prison system… It becomes clear, that the government still very much considered the former slaves and their descendants as property, they could largely do with as they pleased.
Yes, it is intentional. And the “never attribute to malice what you can attribute to incompetence” trope is clearly wrong in the context of politicians.
When they do these things they know what they are doing and who they are doing it for. Imagine an engineer would have designed 10 generations of exploding phones. Would you say it is just incompetence after the third one? So why give politicians the slack to always be “incompetent” in the same way over and over again that just so happens to defend the interests of the oligarchy against the normal people?