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After an awards season marked by its predictability, the Oscars delivered a spectacular final-reel twist on Sunday evening, naming capitalist satire Parasite best picture.

Bong Joon-ho’s comedy-drama about an impoverished family who infiltrate the household of a wealthier one is the first film not in the English language to take the top prize. It also took best director, best original screenplay and best international film.

Sam Mendes’s 1917 had been tipped to rule triumphant at this year’s Academy Awards, following its key victories at the Baftas, Golden Globes and crucial bellwethers such as the Producers Guild Awards. In the event, the harrowing first world war drama took three awards: for Roger Deakins’ cinematography and for its visual effects and sound mixing.

Parasite's best picture triumph could begin a new era for the Oscars Read more

Bong’s film also defeated Once Upon a Time in Hollywood, Jojo Rabbit and The Irishman to best picture. It marks the first time in 65 years – since Marty in 1955 – that the winner of the Palme d’Or at Cannes has progressed to a best picture Oscar.

Bong paid tribute to Scorsese in his best director speech, saying that, when he was young, he “carved deep into my heart” a quote by Scorsese: “The most personal is the most creative.”

He also thanked Tarantino for championing his work: “Quentin, I love you.”

When the film won best picture, Bong gave the microphone to the film’s producers Kwak Sin-ae and Miky Lee. Kwak said she felt “a very opportune moment in history is happening right now”, and Lee paid tribute to Bong, praising his “crazy hair, the way he talks, the way he walks … and especially the way he directs”.

Facebook Twitter Pinterest ‘I love the way he talks, the way he walks’ … Parasite producer Miky Lee on stage at the Academy Awards. Photograph: Étienne Laurent/EPA

She then thanked the Korean cinemagoing public for “never hesitating to give us straightforward opinions that made us never about to be complacent, and to keep pushing the envelope.”

Only 10 foreign-language films have previously been nominated for best picture – including Amour and Life Is Beautiful – but none of them won. Last year, many thought Alfonso Cuaron’s autobiographical drama Roma might take best picture as well as director, but it was pipped to the post by Green Book. That result was not well received, with many people feeling the Academy’s strenuous attempts to diversify were undermined by the celebration of a film whose approach to race relations seems more suited to its 60s setting than to 2019.

Such fallout – coupled with the backlash to the fact only one person of colour (Harriet’s Cynthia Erivo) was nominated for an acting award – could help explain Parasite’s unprecedented win. Voters are eager to prove their inclusivity, and that they don’t fear what Bong called at the Golden Globes “the one-inch-tall barrier of subtitles”.

Almost every person who took to the stage during the ceremony alluded to this year’s dominant controversy, with Janelle Monáe’s opening musical medley seeking to highlight ethnically diverse films, and rapper Utkarsh Ambudkar giving an earnest midway recap of the evening’s inclusivity credentials. Opening presenter Chris Rock made blunt reference to what was missing from this year’s director nominees: “vaginas”.

Lead actor Joaquin Phoenix followed a string of politically charged acceptance speeches – including his attack on the “systemic racism” of the film industry at last Sunday’s Baftas – with an impassioned call to arms, imploring people to stop fighting and to stop exploiting one another, the planet and the other species living on it.

Facebook Twitter Pinterest ‘Many of us are guilty of an egocentric worldview’ … Joaquin Phoenix make’s the night’s most overtly political speech. Photograph: Mark Ralston/AFP via Getty Images

“I think we’ve become very disconnected from the natural world,” he said. “Many of us are guilty of an egocentric worldview, and we believe that we’re the centre of the universe. We go into the natural world and we plunder it for its resources. We feel entitled to artificially inseminate a cow and steal her baby, even though her cries of anguish are unmistakeable. Then we take her milk that’s intended for her calf and we put it in our coffee and our cereal.”

He closed his emotional address by quoting a lyric written aged 17 by his late brother, River: “Run to the rescue with love and peace will follow.”

Phoenix was a much-anticipated victor in the best actor category, for his role as a mentally ill aspirant comedian in Joker; likewise Renée Zellweger being named best actress for her performance in the Judy Garland biopic raised few eyebrows.

The supporting actor races also unfolded as expected, with Brad Pitt and Laura Dern winning for Once Upon a Time in Hollywood and Marriage Story, respectively. Both thanked their parents and their children, with Pitt straying into politics to mention that his 45-second speech was 45 seconds more than the time afforded to John Bolton by the senate in Donald Trump’s impeachment trial.

Elsewhere, Taika Waititi proved a popular presence both on stage – where he dedicated his trophy for best adapted screenplay for Jojo Rabbit to “all the Indigenous kids all over the world” – and backstage.

It was there he offered a commentary on contemporary far-right extremism, saying that, at the end of the second world war: “if you were at Nazi, you would go to jail. Now you’re a Nazi, feel free to have a rally down in the square with your mates.”

• This article was amended on 10 February 2020 to correct the names of the producers of Parasite, Kwak Sin-ae and Miky Lee, who were misidentified as actors in the film; and to remove an error about former national security advisor John Bolton, who was incorrectly described as a senator.