What is it about Citizen Kane that makes it so widely parodied?

I think it's just because there are so many iconic images from that film, it's easy to parody. I don't think most of the things you mentioned are mocking it because they think it's bad. I think it's just ripe for parody because it's so familiar to so many people.

In part, it's because Citizen Kane is often listed by critics as the best film of all time, and Orson Welles' best film...also because the "rosebud" mystery is not expected and comedy thrives on the unexpected, it is a natural fit for parody and satire. Plus, there is the "widely watched" factor that you cited - it's a cultural signpost for several generations - that's why you see so many parodies and satires based on "the Shining"

In my mind, parodies are a tricky subject, sometimes seems to be by respect, some others the opposite. In the case of The Simpsons, is an usual practice to parody dozens of classic films, or art films, some not old at all, in their humour rules, wich personally don't dazzles me. (Although i got kind of laugh when i saw the Citizen Kane parody chapter, even the angles and camera movements were the same.) I would say you parody what you don't understand (look at some of the Razzy awards, for one)or because you want to reverse the dramatic or tragic tension the film could have. Maybe Citizen Kane, because all the visual and optical issues, the technical and linguistical richness is a fertile ground to sow. And on the other hand, when a piece of art becomes an institution, people tries to get it down to the grownd, wich is not always bad.