I'l restrict my answer to Germany, where I can name some names, but the same could probably be said about France and Italy, maybe even the United Kingdom.
During the 1990s I encountered a lot of people in administrative positions with the state that referred to "marching through the institutions" when talking about their careers. But was that the core of their motivation? The 1970s saw a massive increase in personnel in public institutions, be it teachers, social services, or plain bureaucracy. Those who were students in the late 1960s were in a prime position to take these jobs, to hold on to them and rise through the ranks thoughout their working life.
Certainly they did take their political views with them. Certainly that changed the nature of the institutions they were working for. Old timers that had started their careers during the Nazi regime went into retirement. From my viewpoint this was more an expectable generation change than a purposefull "subversion" of capitalist institutions, whatever illusions the actors were under.
And yes, some of those did rise to the top and became prominent. As an example, take the Otto Suhr Institute for Political Science at the Berlin Free University. There were a number of well-known leftist professors that came out of the student movement. A few names: Herta Däubler-Gmelin, Johannes Agnoli, Gesine Schwan, Wolf-Dieter Narr. (This does not say the Institute was dominated by their positions. There always were equally prominent right-wing professors like Arnulf Baring or conservatives like Roman Herzog.)
You will find comparable careers throughout leading positions everywhere in Germany. For me and my friends it was always a tongue-in-cheek game to guess which "K-Gruppe" (communist faction) they were a member of in their youth just from their personality: Former Bolsheviks were loyal followers of every party line offered to them, Maoists you could tell by the complete absence of moral principles, and Trotzkists could argue ideology until hell froze over...
Of course Rudi Dutschke himself, and actually the majority of activists of his generation took a different road. They organized their own movements outside of the established institutions. Green movement, Anti-nuclear movement, house squatters, feminist movement all represent a counter-reaction within the German left during the 1970s. They decided to leave the ideological trenches and hard-set views of the K-groups behind them and move on to more constructive endeavors. Some moved to the countryside, others founded cultural institutions or took the capitalist gains of their fathers and devoted them to a political trust. A small collective of students offering a moving service became one of Germanies largest moving companies. Publishing houses, film distribution and periodicals are a given.
And others founded a political party. Rudi Dutschke was among the founding members of the German Green party. His premature death, a late consequence of the 1968 attempt on his life, prevented him from taking a leading role, but others from his generation were successfull: Joschka Fischer, Daniel Cohn-Bendit, Claudia Roth, Antje Vollmer and a long number of other household names in German politics. Others left the party again, either reaffirming their leftist roots (Jutta von Dithfurth, Rudolf Bahro), joining the social democrat party (Otto Schily) or moving to more conservative politics (Herbert Gruhl).
A curious case is that of Winfried Kretschmann, who was blocked from entering public sevice as a teacher because of his membership in a KBW student group, but is now the Prime Minister of Baden-Württemberg.
And here is a final tidbit: Rudi Dutschke wrote articles for a 1970s periodical called Der lange Marsch. But that paper distanced itself from what they call "social democrat entryism" in favor of a "counter public sphere" (Gegenöffentlichkeit):
"Der 'lange Marsch' wird [...] als sozialdemokratischer Entrismus interpretiert: Jahrzehntelange Unterwanderung und allmähliche Umfunktionierung bürgerlicher Institutionen. Nichts lag uns ferner. [...] 1968 erschien ein vom INFI des SDS herausgegebenes Buch: 'Der lange Marsch'. Sein Vorwort war ein Beitrag zur Strategiediskussion der revolutionären Linken.
Darin sollte die Einheit und der Zusammenhang des Befreiungskampfes der Guerilla in der Dritten Welt mit dem sozialistischen Kampf in den Metropolen aufgezeigt werden.
'Der lange Marsch der Guerilla durch die Kontinente' war die eine Seite der revolutionären Strategie, die andere war der 'lange Marsch durch die Institutionen' in den Metropolen. Der lange Marsch wurde hier verstanden als ein permanenter Konflikt mit den bürgerlichen Institutionen, eine andauernde Provokation bürgerlicher Öffentlichkeit, die Schaffung eines Gegenmilieus, das Selbstveränderung ermöglichte und Veränderung der Verhältnisse kongret in Angriff nahm."
(translated by DeepL)
"The 'long march' is [...] interpreted as social democratic entryism: Decades of infiltration and gradual re-functioning of bourgeois institutions. Nothing was further from our minds. [...] In 1968, a book published by the INFI of the SDS appeared: 'The Long March'. Its preface was a contribution to the strategy discussion of the revolutionary left.
It was intended to show the unity and connection between the liberation struggle of the guerrillas in the Third World and the socialist struggle in the metropolises.
'The long march of the guerrillas through the continents' was one side of the revolutionary strategy, the other was the 'long march through the institutions' in the metropolises. The long march was understood here as a permanent conflict with bourgeois institutions, a continuous provocation of bourgeois public opinion, the creation of a counter-milieu that enabled self-change and concretised change in conditions."