Complex sentence: This meant that the Nazis' aim of staging a show trial became futile, so Hitler ordered the killing of the "special security prisoner Eller", the name by which Elser was called in Dachau.
Split into simpler sentences: This meant that the Nazis'intention of staging a show trial had become futile. Therefore Hitler ordered the killing of special security prisoner' Eller', that being the name by which Elser was called in Dachau.