Do you know what type of leather it is?
Have you looked at it through a microscope?
Did you apply degreaser and leave it long enough to turn to powder?
If it turns to a white powder without any trace of brown in it (grease) then that's it as far as getting the grease out goes. Remember is strong enough to remove some of the colourant from the leather too.
If it's gone rough then the chances are it's starting to delaminate which means removing as much of the loosened coating as it will allow, clean, sand it down smooth, leather prep to remove all the top coating (the whole panel) and then build back up with the correct colour, recoat with suitable finish, apply protector cream.