This is from 2011 but I only just read it.
One explanation for why Germans are not funny inlcude
Many jokes in English also rely on wordplay and deliberate verbal confusion, while the greater precision of German perhaps makes it harder to engineer such confusion.
This might be why Germans like physical humour. “One of the iron rules of Germany comedy”, Henning When explains in a video on German jokes, is that “physical humour is best… An old codger [guy] falling over or getting a cake in the face is always funny… even during a famine.”
You can read the rest (including the rankings) here.