Per Barbra Leaming's book, Paul Masson switched from Welles to John Gielgud as spokesman in order to emphasize thier new low-cal wines. But of course, Welles showing up on the Masson set too shitfaced to work couldn't have helped his cause either.
What I find interesting about Welles' commercials is the fact that he only did them for food, drink, or entertainment, as far as I know. I don't know if he ever did one for any industrial product like, say, tires or batteries. I suppose that, given his size, he got pegged as a food and drink man, but in general, his world viewpoint seemed vaguely opposed to industrialism anyway.