A good introduction to the Heidegger case:

How the same man could be one of the greatest 20th century thinkers and lack so much political and moral discernment? Heidegger epitomizes the case of many philosophers of the time who could not accommodate with the reign of the “last man” and end up with the “secular religions”, either Fascism or Communism. At this level, Guenon’s apolitheia was the exception rather than the rule.

In the case of Heidegger, one may wonder if the religious character of his thought, the fact that it presents itself as a religion but without revelation, did not contribute to his political”mistake”. This approach may provide an alternative to the “heideggerian orthodoxy” which has tried to account for his involvement with Nazism in term of a still incomplete overcoming of the “metaphysics of subjectivity”.