Reconstruction failed to bring equality to the freed slaves because it would have been very hard to bring them equality even if the government had had more power and will than it actually did.
Right after the war, the freed slaves were inferior to whites socially, politically, and economically. It would have been exceedingly hard for the government to have fixed all of these things. There was no way that governmental fiats could have made blacks and whites equal on a social basis. They might possibly have been made equal in the eyes of the law, but whites were simply not going to see blacks as their equals. It would have been very hard to make the African Americans economically equal to whites. They lacked education. They lacked land to farm on and it would be legally and politically very difficult in our system to take land away from the plantation owners and give it to the slaves. Political equality was easier to give since it involved only allowing African Americans to vote.
Even if these things could have been achieved, they would have taken effort on the part of the government. It took a military occupation of the South to even get blacks to be granted political rights. The North was not willing to continue to occupy the South just to accomplish this. Because of this lack of will, Reconstruction ended and blacks were still not equal to whites on any level.