On page twenty one of Adolf Hitler: A Biographical Companion by David Nicholls he notes how the judges sitting in The Austrian Corporal's trial were if not Hitlers followers then the facts support broadly right wing, authoritarian, anti Semitic (although even in Britain a high percentage of people were circa 1930) anti communist, and not satisfied with the end of the war or Weimar regime and so sharing Hitlers ideology barely bothered to hide their disinterest in the maximum sentence from the start (death) and bumped it down to a petty four years although he was released earlier as you say.

Essentially the Generals judging had the back of the FreiKorps (ex soldier militia) so no matter how corrupt Hitlers trial was noone had the forces or willpower to stop it as the Weimar Republic realllllly was very clear on not fancying a civil war.