Why would Janeway even accept promtion? Wasn't she in love with the thrill of command and exploration?
Its not like she couldn't have gotten another command in the aftermath of the Dominion war staffing shortages.
Moving up the admiral ladder is for grey hairs before you retire.
i like the theory it was a token desk job to keep morale up instead of revealing all the terrible and bizarre things janeway did in the delta quadrant.