The following passage is from Steiner's Martin Heidegger

Being and Time is written during the early 1920s. It comes, as I have said, of the apocalypse of 1918 and of the Expressionist climate. It fully predates National Socialism. No Nazi hoodlum, to my knowledge, ever read or would have been capable of reading it. The crux, made more complex by the problem of Deconstruction and of such post-Heideggerians as De Man, is this: are there in Heidegger’s incomplete ontological summa categories, advocacies of inhumanism, eradications of the human person, which, in some sense, prepare for the subsequent program of Nazism? Is Heidegger’s play with and on Nothingness (a play intimately analogous with negative theology) a nihilism in extremis rather than, as it professes to be, an “overcoming of nihilism”? Assuredly, Sein und Zeit and Heidegger’s theory of a language that speaks man rather than being spoken by him is utterly seminal in the modern anti-humanistic movement. There is little in Deconstruction or in Foucault’s “abolition of man,” with its background in Dada and Artaud, which is not voiced in Heidegger’s a-humanism — where the privativum of the prefix does seem to me more accurate and just than would be that of in-humanism. Secondly, there is the famous urgency of death, of the will to and motion toward death in Heidegger’s analysis of felt being, of human individuation. Rooted in Pascal and in Kierkegaard, this death-insistence does, by virtue of the fact that it attempts to free itself from theological contexts, carry a heavy charge of negation. Can we say that this weight inflects Heidegger’s and his reader’s attitudes toward the macabre obsessions of National Socialism? I see no ready answer to either of these questions. Post hoc is not propter hoc. Books of the difficulty and singularity of Sein und Zeit do not, in any immediate or programmatic way, exercise their effect upon politics and society. It may indeed be the case that Heidegger’s tonality, that Heidegger’s charismatic regency of certain circles of intellect and of sensibility in the Germany of the late 1920s and early 1930s did contribute to the ambience of fatality and of dramatization in which Nazism flourished. Intuitively, such a conjunction seems plausible. But it could only be demonstrated if specific texts in Heidegger’s magnum could be shown to have generated dependent motions of argument and of action in Hitler’s rise to power. No such demonstration has, despite attempts by such critics of Heidegger as Adorno and Habermas, carried conviction. It could well be that we stand too near the facts. Darkness can blind as sharply as light; and the two may take centuries to untangle (consider the debates which persist over the politics and the impact on politics of Machiavelli or of Rousseau. — Steiner

Steiner believes that the real Heidegger is not accessible from any of his writings. He apparently had some sort of charismatic presence as a lecturer, and if you never heard him, you're clueless.

Being and Time is rather a failed (according to Steiner) attempt to arrive at some sort of new and irrational comprehension of Being. All the neologisms and piles of words are meant to clear the rational clutter that blinds us to the being of Being. In this, it's kin to Surrealism, which seeks to bypass the intellect and express a higher truth.

And both Surrealism and Heidegger are a kind of stress response to the end of WW1. Steiner says this period in German history is a catastrophic collision with nihilism. Where the period after WW2 was a deafening silence, the time between the wars was a desperate attempt to rise above a dark godless defeat, manifesting as apocalypticism.

The question is: did this longing to ditch rationality turn into in-humanism that set the stage for the Holocaust?