I believe Kerry had help getting into the Navy since it was so hard to do at a time when so many were facing the draft into a ground war. I remember well how some of my classmates tried and failed to get in the USN. So it should be in his records that someone influential, perhaps just his father, (perhaps a Kennedy?) was someone that would complain if Kerry were cashiered out as he deserved to be. So give him some Purple Hearts, some Stars and send him home to run for office as a war hero.
Something planned surely occurred. For someone that volunteered for Viet Nam duty to serve his country, four months of that sought-after duty would not be much of a fulfilment. Especially in light of the serious nature of the three purple heart wounds which lost him all of one day of "incapacitation"(I suspect less than 1 hour). And the fact that prior to his release from military duty he was gallivanting around the country doing anti-war activities.