Martian: yes, Carson wanted Letterman to take over, and NBC screwed him over and signed Jay Leno instead.
Jay Leno was a douche before NBC though:
What's crazy is that Leno's ratings aren't going to be nearly as good as they used to be because of this fiasco, and he's not gonna be on there forever. What does NBC expect to do in 10 years (if it takes that long) when Leno leaves The Tonight Show
again? Letterman will be gone, Conan and Craig will have no interest in NBC, and Jimmy Fallon sure as hell won't be the next host if they have any sense (not that there's any evidence they do). This whole thing represents a
complete lack of foresight on their part.