I can't see it butterflying away the popularity of Citizen Kane, such is the stature of that particular film. But old Orson probably wouldn't be in demand for Don Masson and
Dark Tower ads decades later.
On the plus side, it might jettison his participation in the fundamentalist schlockfest The Late Great Planet Earth.
There's more than Kane and selling out. Orson Welles was extremely prolific. And his ad man period was huckstering for money to get his films made. He made "The Magnificent Ambersons", "Touch of Evil", "The Lady From Shanghai", "Chimes at Midnight", "F for Fake", and was part of "The Third Man", alongside Joseph Cotten who never would have made it without Kane. Also, Citizen Kane was successfully buried under by William Randolph Hearst at the time. It was only in the 1950s, with the rise of the French New Wave and a modern era of film that the film was reassessed as being as important and groundbreaking as it was. You had people with that feeling at the time, but the culture somewhat buried it until the 1950s. Frankly, it was buried alive by Hearst, his campaign against the film, and newspeople and actors who did not understand they were the force of power and not the newspaper tycoons. Hearst was less important and influential than someone like Clark Gable, but Gable wouldn't understand that, for example, and assume the reverse.