@odd I kinda knew the downhill story - ( i recall someone once summarized his career - a total 180 to most people in film - who start with ads and grow into a masterpiece - and welles did it the other way round) - but I never thought to explore how or why ... but your reply sounds about right - a quick check in quora - and voila - you are onto something ..

I particularly liked this one

Mark L. Levinson Occasionally translates for the film industry
Maybe Daniel Poissant is right that the anger of William Randolph Hearst is responsible. See The mystery of Rosebud - explanation: Gore Vidal, in one of his less forthright moments, claimed that Rosebud was Hearst's name for his mistress Marion Davies's "tender button", and that this was the real reason for Hearst's objection to the film. Vidal is cagey about the source of the story, though he knew Marion Davies, and Mankiewicz was well acquainted with both Hearst and Davies.
There was also the matter of It’s All True, the project for which Welles was accused of wasting far too much film on location shots in Brazil. They say the real objection wasn’t the amount of footage, it was the amount of footage that was considered unusable because it showed dark-skinned and light-skinned people having fun together.