I'm thinking the Justice Department has discretion on what cases and how hard they fight, and they might not want the particulars of this case dragged back into the limelight.
If they basically "no contest" it, they can frame it as another "Orange Man Bad", his dishonorable discharge gets converted to a General discharge (I think) and the story disappears in a week or two.
....
Or we can argue about undue Command influence and drag the deserter's whole story back out in front of the country, and maybe look up what those 5 fine people Mr. Biden helped release have been up to since.