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Elie, as did all the Jews of Sighet, recognized Hitler's hatred of the Jewish people. They understood the threat posed by the rise of the German Fascist party, but they considered it too far away from Sighet to ever affect them personally. Night is the record of how wrong they were and of what they went through as victims of Hitler's actions.
A rationale is "the fundamental reason or reasons serving to account for something." Night was not written to present the reason(s) why Hitler determined to eliminate the Jewish people from existence. Instead, it was written to witness to the horror of what was done, to remember those who died, and to recognize the strength of those who survived the Holocaust. So by this analysis, no, Wiesel does not present a rationale for Hitler's actions.