We are waiting in an age that believes in symptoms of malaise. We wonder if we might be slipping. The picture business feels dead on its feet. So it’s easier to suppose that the new movie, Mank, was made out of a kind of death wish. Does director David Fincher, or Netflix, really think that audiences are going to care about the California gubernatorial election of 1934, or pick up all the name-dropping the movie indulges? Why is it David Fincher if no one gets murdered? Why the screen time for Louis B Mayer, Irving G Thalberg and David O Selznick – middle-initial celebs the audience can’t place? And why has the demented project hired a 39-year-old actor, Tom Burke, to play Orson Welles, who was 25 in 1940, when it mattered?

You have to start with the prodigy named Orson. Finished with formal education by 16 (in 1931), the kid from Kenosha, Wisconsin, had soared. By 1938, he was infamous, and loving it. He had co-founded the Mercury Theatre (with his dear friend, John Houseman); he had mounted a Harlem production of Macbeth, done as a voodoo rite; he had directed and acted in Caesar (as in Julius) and Heartbreak House (playing a man in his 80s); and he had been the guiding radio voice – baritone, seductive yet often on the edge of bogus – for the Mercury Theatre of the Air. It was in that capacity, at Halloween 1938, that he spooked the nation with a version of HG Wells’s The War of the Worlds, in which gullible chumps could believe New Jersey was being invaded by Martian zombies.

Welles was besieged with offers from Hollywood to make a movie – almost any movie, and on his own terms. He knew it all. He was a maestro. “There but for the grace of God, goes God,” people said – or was it the mischievous Welles who said it? In that dense, paranoid club, Hollywood, he was loathed, feared and envied.

Then he bumped up against an obstacle. Granted carte blanche for his movie debut, he couldn’t decide what to do, or how to write it. He grew frustrated and angry with this dilemma, and he was a large boy with a frightening temper. There was a furious fight at Chasen’s restaurant where Welles threw hot dishes at Houseman. This ended the most sustaining working relationship Orson would ever have. Houseman was highly creative though overawed by Welles, and half in love with him – maybe two-thirds – and he is presented in Mank as a fusspot stooge.

Houseman was suddenly an outcast. Whereupon, Welles thought to enlist Herman J Mankiewicz as a rescuing screenwriter. Mank was 43 in 1940 (Gary Oldman is 62). He was brilliant but washed up, a famous wit and a chronic drunk. He had never written anything remotely like Citizen Kane – and he never did again – but he was intrigued by the scheme of a film about a great American achiever, just as he was fascinated by the outrageous, childlike Orson.

Orson was full of ideas (and it was a given that he would play the great achiever). But he guessed the writing would be better done without his presence. Mank had had a driving accident. With a leg broken in three places, he needed bed rest. Thus a lovely setup was devised: Mank would be shipped off to a desert ranch with a good secretary to write a draft of the script. But there were worries: Mank was incorrigible, adept at finding booze in a desert, and not exactly disciplined. He needed looking after. The idea arose – and it had to come from Orson or have his approval – that Houseman might be the ideal caretaker at Rancho Verde on the edge of the Mojave desert. If his wounded love could be wooed back again.

Houseman consented, and I think he realised that Welles wanted him for one devious reason: that the great achiever in their story would be based on Orson. Later on, the legend spread that the figure resembled William Randolph Hearst. There were several touches of Hearst in Kane. But the notion of a dazzling, arrogant talent – an outstanding performer – was a reflection of Orson’s seething ego. And he knew that no one knew that guy better than Jack Houseman.

There would be fierce arguments over who wrote what: Orson and Mank shared the writing credit, and the only Oscar Kane received. That argument over authorship goes on. But the situation is of three pretenders and manipulators playing a kind of chess. There is no reason for this film now without it grasping that reckless game.

Instead, Fincher idles away two hours with stuff that doesn’t matter – a feeble, confused and tiresome gloss on what Hollywood was like in the late 1930s, instead of an explanation of how this extraordinary, subversive film came into being.

• Mank is released in cinemas in the US now, in the UK – excluding England – on 20 November and on Netflix from 4 December