Kane was voted greatest film in the Sight and Sound survey in 1962, but Welles completed the Trial, Chimes, Immortal and Merchant after that, so I'm not sure it was Kane. But I do think all the books being written possibly had a paralyzing effect, a process of becoming very self-conscious. By 1972, we had maybe 6 books on Welles, including the French ones (Fowler, Noble, Cowie, MacLiammoir, Bessy and Bazin). But very quickly in the 70s the whole middle-class film awareness/film school develpment/university film courses/ books on film/ film magazines scene exploded, and I do believe that had an effect on Welles: very soon there were more books on him than films. and we do know he became very upset and distressed by three books published in quick succession at the beginning of the 70s: Higham's first in 1970, with the "fear of completion" theory, Kael's in 1971, which claimed that Welles did not write Kane, and Houseman's in 1972, which was highly critical of aspects of Welles's character. Perhaps on some subconscious level he also didn't want to screw up an almost perfect ouvre, increasingly solidified (calcified?) by the dozens of books and hundreds of articles, etc. I recall McBride writing that the seashell dropped by Charles in Immortal Story's final scene was the bookend to Charles dropping the snow-globe in Kane, and I remember thinking that was so beautiful. And Welles never finished another dramatic film after Immortal, unless you count the finished Merchant which had a reel stolen.
Glenn Gould was fond of referring to interview questions that dug too deeply into his method as "centipedal" questions: he recounted the story of the centipede who, happily walking along one day was asked by another insect "In which order do you move your legs?". When the centipede tried to figure out the answer to this question, he promptly became confused, fell over and could no longer walk.
Maybe Welles became like that centipede in the 70s and 80s, on a very subtle level, though this does put one in the uncomfortable camp of dime-store psychology and the "fear of completion" theory of Charles Higham.