coolandsmartrr
Karl Jasper's role in developing existentialism is noted well in "At the Existentialist Café" by Sarah Bakewell[0].

He's also known as the mentor of Hannah Arendt, who later wrote "Origins of Totalitarianism", "The Human Condition" (Alan Kay's favorite book[1]) and "Eichmann in Jerusalem" (served as basis of her 2012 biopic[2])

[0] https://www.amazon.com/dp/1590514882

[1] http://www.squeakland.org/resources/books/readingList.jsp

[2] https://www.imdb.com/title/tt1674773/

midoridensha
The Frank Herbert book 'The Santaroga Barrier' has a psychoactive substance (much like the "spice" in his Dune books) called "Jaspers", named after Karl Jaspers:

https://en.wikipedia.org/wiki/The_Santaroga_Barrier

Gabriel54
At least Monty Python knew Jaspers: https://youtu.be/LfduUFF_i1A
divyaranjan1905
He isn't really forgotten in the academic circles who deal with the history and philosophy of existentialism. Jaspers is very well remembered along with Kierkegaard, Sartre, Camus and others. But yes, at the 'general public' level, he isn't really forgotten.
pram
Is he really that forgotten? Camus talks about him in "Myth of Sisyphus" and while I haven't read his work personally I definitely recognize his name from the "existentialist pantheon"
sr.ht