Absurd article by NYT.
According to this https://en.wikipedia.org/wiki/Beer_Hall_Putsch#Trial_and_prison it was not really a prison.
He got five years but got out after some eight months. During that time he also dictated his Mein Kampf book to Hess and another of his allies. See also the photo in that article of a "cozy" meeting in the "prison".
The lay judges were fanatically pro-Nazi and had to be dissuaded by the presiding Judge, Georg Neithardt, from acquitting Hitler outright.[42] Hitler and Hess were both sentenced to five years in Festungshaft [de] ('fortress confinement') for treason. Festungshaft was the mildest of the three types of jail sentence available in German law at the time; it excluded forced labour, provided reasonably comfortable cells, and allowed the prisoner to receive visitors almost daily for many hours. This was the customary sentence for those whom the judge believed to have had honourable but misguided motives, and it did not carry the stigma of a sentence of Gefängnis (common prison) or Zuchthaus (disciplinary prison). In the end, Hitler served just over eight months of this sentence before his early release for good behaviour.[43] Prison officials allegedly wanted to give Hitler deaf guards, to prevent him from persuading them to free him.[28]