Less than a generation after the US fought the bloodiest war in its history to eradicate slavery, the south had reestablished a racist legal power structure that sabotaged the hard-fought reforms many had died for; why did the north let them do it? Did it provoke outrage/protest?

So what you are asking about intertwines into the larger milieu of the post-Reconstruction Redeemer movement and the Lost Cause. I've written a few things in the past here that touch on the matter, so I'm happy to link you to a few relevant responses, some further readings, and of course field any follow-ups you have best that I can!

This answer, and the follow-ups to it, would be a good start I think. It looks at 'why the North let them', analyzing commemoration of the Civil War from roughly the point of the 25th anniversary onwards, and illustrates how elements of the Southern narrative of the war, the 'Lost Cause', was allowed to become part of the national narrative in the interest of healing and national unity, but how it was "a vision of a reconciled nation premised on forgetting slavery". I'd also point here which looks at commemoration in the South specifically.

I'd also point to this subchain in a marginally related thread where /u/sunagainstgold and I run through some of the issues present in the political landscape during the early Jim Crow era, and which I feel flesh out the above a bit more.

I'll finally make quick reference to this answer which looks at the elections in the Reconstruction era and beyond, although it is more for background.

Finally, I'd direct you to my very extensive "Lost Cause Reading List". It is long, though, so for the specific focus here, I would note that Blight, Blair, Janney, and Foster would be the best options for book length treatments. Janney's "Remembering the Civil War" especially dives deep into the reconciliation angle (It is, afterall, subtitled "Reunion and the Limits of Reconciliation").