To respond to the problem of laughter in response to already known jokes, I think the guiding principle behind such reaction is in contrast of seriousness. Incongruency itself isn't funny on it's own, but when you add a grounded or serious context to it, it starts to gain shape.

In Monty Python (which this article refers to in notes), extreme care was put into making it look authentic at a glance, but they carefully break that serious setting to introduce humour. If you take a look at sitcoms, they do the same thing in principle, just focus it on different elements.

Expectation is a part of humour but not the whole story. Comedy is about contrast. Contrast between the elements and the personal experience of the individual is what allows this funny business to exist.