Heidegger’s interest in transforming the university began relatively early in his career. For example: In a passionate letter to Karl Löwith, August 1921 (Heidegger was already 31!), he was very intent that...
the old university cannot be overcome [through merely replacing] the “intellectualism” of fossilized lecturers [with] individuals whom one considers to be richer, more lively, and deeper; instead it can be overcome only by returning to the origins of action in what has survived in contemporary facticity and by deciding for oneself what one can do....we [are to] sacrifice ourselves and find our way back into our existential limitation and facticity rather than reflecting our way off into programs and universal problems....That sentiment, five years prior to Being and Time, would gain vast elaboration in later years (and live with embittering disappointments). Even his 1946 “Letter on ‘Humanism’” begins with the concept of action. Throughout his career, he was practically oriented. [The 1921 letter is reproduced in the back of Löwith’s book Martin Heidegger and European Nihilism, 1984 (English 1995).]
Since German universities understood all of their faculties of sciences and humanities as “Philosophy Faculty,” and the university was the training ground for government mandarins (the original purpose of the German university!), Heidegger’s engagement with transforming philosophy throughout the 1920s is implicitly attention to his passionate desire to overcome the “old university.” In Being and Time, the 1921 sentiment isn’t elaborated in terms of university reform, but B&T shows a communal sense of action that Heidegger applies later only in terms of university reform.
His communal sense of emancipatory action has been made clear by Theodore Kisiel (which I’ve referenced in the past so often that this might seem tiresome now):
• pp. 1-7 of “...Heidegger’s three concepts of the political”
Heidegger’s 1933 enthusiasm for “self-assertion of the German university” was based on a grassroots, communal sense of potential for political economic renewal that had nothing to do with actual German national politics. He thought that the universities could be the basis for national economic reform (at the height of the Depression), and he sought to lead a local and regional coordination of universities that would shape Berlin educational policy. This is why he accepted being elected to the rectorate position (which he didn’t seek). Every note of enthusiasm for a “national socialist movement” was relative to his long-held hope for university leadership in economic recovery after the 1929 Crash.
When he gave an expansive lecture on university reform at Heidelberg University, end of June, 1933 (more than a month after his “Self-Assertion...” speech as Rector of Freiburg University), there was no reference to Nazi Party policy. But there was passionate expectation that university policy reform would affect Berlin policy (bottom-up thinking) that had not yet crystallized for Berlin. One should keep in mind that, in early 1933, there was no presumption that the vast bureaucratic structure of German education could be immediately dominated by Nazi ideology. Thinking that grassroots initiative vis-à-vis the mandarin German state could be fruitful was hardly unrealistic—though he was working with the university faculty he had to work with, many of whom were Party supporters. (What is one to do about that constructively?)
After that Heidelberg lecture, at a faculty dinner, Heidegger was criticized for not referring to Nazi Party aims. (Shortly after the dinner, Heidegger reported this event to his good friend H. W. Petzet, recounted by Petzet in his Encounters and Dialogues, 1993.)
But Karl Jaspers missed the fact that Heidegger was working for bottom-up reform, i.e., alignments from university-based coordinations to regional policy, regional policy to Berlin. What Karl Jaspers heard at the Heidelberg lecture reflected Jaspers’ proper fear of top-down alignment, which Heidegger never intimated.
That is why Jaspers thought that Heidegger was a Nazi. But Heidegger was actually working to have regional universities follow his lead, not have universities follow Berlin’s lead (or rather—unrealistically—Heidegger wanted university leadership to decisively affect Berlin educational policy). Jaspers did not understand Heidegger’s communal approach to change—warranted by Being and Time, an approach which was obviously being improvised in 1933—and Jaspers mistook Heidegger’s constructive engagement with regional administration as an effort to collude with Berlin’s efforts (and then, so did so many later scholars who relied on Jaspers’ view).
In fact, Heidegger resisted Nazi efforts at every opportunity while he was Rector, not just getting critical after quitting in disgust. In August, 1933, he wrote to Carl Schmitt that he was “depressed” about what was happening. In September, 1933, he wrote to Elisabeth Blochmann that he had just returned from a weekend at The Hut where he was considering resigning from the rectorship—five months into the job.
Heidegger’s efforts of constructive engagement were fated to fail, but his attempt is no evidence of collusion. A habitual mistake of scholars considering Heidegger’s administrative time is to expect that lack of public opposition signals private acquiescence. But obviously, overt oppositional activity was self-destructive (and his “black notebooks” obviously document his bitterness in late 1933 onward).
Throughout critical philosophy in the 20th century, a hegemony of the negative dialectical paradigm (which equates [a] lack of dramatic opposition and [b] acquiescence or appeasement, if not affirmation) has perpetuated blindness about how non-collusional constructive engagement may work to change others’ practices by working with the misguided other (e.g., in remedial parenting, teaching, counseling—and realpolitik). Non-collusional constructive engagement is not appeasement (let alone duplicitous collusion). [When one could be jailed for not saying “Heil, Hitler”—a law imposed July 1933—it’s good to play along with what became a casual joke; circa page 29, I believe—see “Hitler salute“ in the Index.]
Jaspers’ misunderstanding of Heidegger’s emancipatory (constructively deconstructive) approach to action in teaching became decisive after the war. People made careers, based on Jaspers’ caricature of Heidegger as “mystical” thinker (which was Jaspers’ label in his statement to the De-Nazification Committee, 1945).
But Heidegger never thought that Jaspers understood him. Heidegger unwittingly disclosed that to Jaspers in 1929, when Jaspers heard from a student that Heidegger was making fun of Jaspers’ “philosophizing” in Heidegger’s discussions with some students; and Heidegger later apologized to his friend (not denying that he was dismissive of Jaspers’ views). [This is recounted by Jaspers in the letters between Jaspers and Heidegger, p. 281.]
Then, we see in the Considerations (Überlegungen, “black notebooks,” English edition: Ponderings) that Heidegger is often dismissive during the mid-1930s about Jaspers’ “philosophy of existence,” while Jaspers refused to speak to his friend of 13 years after that one June 1933 evening at a lecture in Heidelberg, not giving himself a chance to believe otherwise about Heidegger.
Then Jaspers’ bias became “common sense” for many “scholars” who were apparently relieved that they didn’t have to really dwell with what Heidegger was trying to do (which is an old discussion by now—part of a larger project—but may be news to some).