The Southern elite did not accept the outcome of the war.
They accepted that aspect of the war's outcome which the North really cared about.
They changed tactics. Slavery may have been eliminated, but semi-slavery in the form of share cropping, voter intimidation, terrorism, and ultimately Jim Crow laws show the elite's power remained alive and well. After 'victory', the Unionists needed to address the issue of large populations of freedmen in the South. These people needed security, access to education and economic development. The Southern elites were not going to provide for these newly freed slaves. The Southern elites, and many other American whites, considered the negro as sub-human. How are you going to change that mind set?
Why should they bother to do anything about it. Many of them agreed with it.
As recently as Nov 1864, over 44% of Northern voters cast ballots for a party which was willing to let the South keep
Slavery (never mind trivia like Jim Crow) if only it returned to the Union. And even many of those who voted for
Lincoln probably did so as they had more confidence in him than in Mac to bring the war to a successful conclusion. IOW they voted for him
despite his views on slavery, not because of them.
The North got everything it fought for. No breakup of the Union, no slavery in the territories, no slavecatchers hunting down runaways in northern streets. Why should they object to the South's elite remaining in power, now that it had conceded everything they really cared about?