For all the piles of research and miles of column inches that have been devoted to it, the controversy over the creative authorship of “Citizen Kane” — a kerfuffle that’s now 50 years old, and one that’s been given new heat by the release of David Fincher’s “Mank” — would seem to revolve around a relatively simple question:

Who wrote “Citizen Kane”?

Was it Herman J. Mankiewicz, the brilliant, witty, slumming, past-his-prime, usually sloshed screenwriter played with dissolute droll charisma by Gary Oldman in “Mank”? Or did Orson Welles, the velvet-voiced boy-wonder genius-egomaniac who wound up splitting the screenplay credit with Mankiewicz, fully earn the right to that co-credit? Did Welles contribute enough of the structuring, editing, and — yes — writing of “Citizen Kane,” and did enough of the film’s animating ideas descend from him, to make the suggestion that Mankiewicz was the hidden engine of the movie a canard?

In fact, the answers to all this were nailed down long ago, by Robert L. Carringer in his 1978 article “The Scripts of Citizen Kane” (which became absorbed into his riveting book “The Making of Citizen Kane,” published in 1985) and by sources like Peter Bogdanovich in his eye-opening 1972 Esquire magazine piece “The Kane Mutiny.” Both offer definitive evidence that Welles was intimately involved in the writing of “Citizen Kane.” And both serve as a rebuke to the writer who first lit the controversy on fire: Pauline Kael, the great film critic — to me, she’ll always be the greatest film critic — who in her 50,000-word essay “Raising Kane,” originally published in The New Yorker in 1971, made a rare fatal blunder by fudging facts and systematically overstating Mankiewicz’s contribution to the movie.

In other words…done and done. Case closed. End of controversy.

But not really. Because even once you accept that Orson Welles did deserve the co-screenplay credit for “Citizen Kane,” there’s a question that lingers, and it’s the mystery that I think Kael tried (unsuccessfully) to poke at. Kael’s essay, among other things, was a kind of backhanded meditation on the inner meaning of what a screenplay is. And the reason that question creates such an endless conundrum when we think of “Citizen Kane” is that “Kane” was the Hollywood movie that changed the answer to it.

If you believe, as I do, that “Kane” is the greatest movie to have come out of classic Hollywood, and maybe the greatest movie ever made, and then you ask, “Okay, but why is it the greatest movie?,” the answer is 50 reasons at once — the visionary excitement of it, the through-a-snow-globe-darkly gothic majesty of it, the joyous acting, the hypnotic structure, the playfulness, the doomy haunting mythology of Rosebud, and on and on and on. The pleasures and profundity of “Kane” are right there on the surface, and infinitely deep beneath the surface.

But what sometimes gets lost in film history, especially for those of us born decades after “Kane’s” premiere, is that the consummate audacity of the movie, the thing that continues to make it such a singular and bracing experience, is that in its inky-shadowed, looming-ceilinged, boundlessly inventive and imaginative baroque showman’s way, “Kane” was a Hollywood movie that subverted the cosmos of Hollywood. It leapt ahead to an age when movies would be wedded to social and psychological reality in ways that the studio system never fully had room for.

I don’t say that as an insult to classic Hollywood. Hitchcock and Capra, film noir and MGM musicals, Bette Davis and Vivien Leigh, Clark Gable and James Stewart — to me, they’re as good as it gets. Yet just as you can acknowledge that and still point out that Marlon Brando brought a lightning flash of authenticity to the big screen that revolutionized movies, “Kane,” in a different way (and nine years before Brando’s film debut), brought a similar lightning flash. Only Welles was so far ahead of his time that the movies would have to wait years to be influenced by him. In 1941, the year of “Kane,” most movies were conceived in two dimensions, good movies sometimes achieved three dimensions, but “Kane” was a four-dimensional media-wise shadow play of the real. It used the life of the media tycoon William Randolph Hearst in such a knowing and immediate way that it seemed to break down the wall that separated life and art.

A good dollop of that came from Mankiewicz, and that’s the subject of “Mank”: how in addition to drinking and gambling, he spent the ’30s hobnobbing with Hollywood power brokers, soaking up the tricks of their trade — the way they charmed and manipulated and terrorized, bending the world to their whims and wills. And, of course, Mank got to know Hearst and his silver-screen inamorata, Marion Davies. He glimpsed their lives from the inside (he was friends with Davies, and saw the gilded cage she lived in), and he drew on all of that in his portrait of life inside Kane’s castle, Xanadu (a gloss on Hearst’s fortress of San Simeon).

The word “gossip” doesn’t exactly evoke art, but Mankiewicz, in using what was basically gossip to fuel the story of Charles Foster Kane, foresaw the Age Of Reality — not reality TV, but the age when movies would begin to shape and reflect the world around them, rather than a rarefied Dream Factory confection of good and evil. One of the messages of “Mank” is that Mankiewicz, in scripting the epic first draft of the drama that was originally entitled “American,” could only dare to write such a script because he had nothing to lose.

But what would “American” have looked like without Orson Welles? Early on, “Mank” shows us Mankiewicz writing one of the narrator’s lines from the News on the March faux newsreel sequence that kick-starts “Citizen Kane.” Did he actually write that line? Maybe so. But the News on the March sequence is one of the most astonishing nine minutes in American film history. There had never been anything like it — an intricate documentary, full of lurching tonal shifts and contrasting film stocks, embedded inside a big-scale movie. That sequence plants us inside the real world, the same way that Welles’ staging of “The War of the Worlds” as a radio broadcast of an actual alien attack planted H.G. Wells’ sci-fi saga in the real world. The Welles aesthetic — and the reason he fought Hollywood from the get-go — was rooted in his reverence for a transcendent reality. (Just watch the restored version of “Touch of Evil,” a noir that revels in its empty-cantina-and-lonely-telephone-wires bordertown squalor and grunge.) Welles sought a movie art that flowed in and out of the life around us. Twenty years before John Cassavetes, he was the first American independent filmmaker.

The discussion about the “Citizen Kane” screenplay is really a way of asking: How did “Kane” acquire its quality of (magical) realism? Who gave it that essence? The short answer is: Orson Welles. The slightly longer answer is: Welles, with a major contribution from Mankiewicz — and, of course, from his other collaborators, like the cinematographer Gregg Toland and the composer Bernard Hermann. Both answers are true, and Welles, in fact, was not a credit hog. He initially fought Mankiewicz on the “Kane” credit, asking for sole credit himself, because his contract with RKO demanded it. The arbitration that resulted in the co-credit was a primitive version of the arbitrations that now go on routinely. “Mank” makes a point of the fact that it’s set during the early, formative days of the Screenwriter’s Guild, when Hollywood writers were setting out to establish not just their power but their identity.

Writers in Hollywood have always struggled for prestige, but they acquired more of it over the last 50 years than they possessed under the studio system, where they were generally considered hacks with a knack. That system meant that they often didn’t get credit, which was fine with most of them (like Mankiewicz), because they got paid. Part of the controversy over the writing of “Citizen Kane” relates simply to the ways that the times have changed. It’s far more conventional today to see a director get a co-screenplay credit — going back to, say, Francis Ford Coppola’s credit on “The Godfather,” which is an apt comparison, since “The Godfather” is the greatest American film since “Citizen Kane.” Mario Puzo contributed at least as much to that movie as Herman Mankiewicz did to “Kane,” yet no one begrudges Coppola’s contribution.

The issue with “Kane,” however, is that the contribution of writers was at that point habitually underrated. And Mankiewicz, in his script, aimed high. He deserved to be celebrated the way that “Mank” celebrates him. Yet Fincher’s film, in trying to salute Mankiewicz’s contribution, winds up echoing the Kael line and giving Orson Welles short shrift. He comes off as a petulant manipulator obsessed with lionizing himself. The film, in fact, would have done better to show us the genesis of “Kane”: the meetings that Welles and Mank first had about it, and how they sparked each other. Yet I understand, in a way, why Fincher didn’t include those scenes. He wanted it all to have a touch of mystery. It means something, I think, that the issue of who lit the creative fire of “Citizen Kane” is not something you can totally pin down. The chemistry of movies is more enigmatic than most of us know — more, even, than filmmakers know. We know, more or less, who wrote “Citizen Kane.” What we’ll never know is how the lightning got in the bottle.