In December, Okwui Enwezor wrote to me from Munich. He had leukemia. ‘What I miss most,’ he said, ‘is the noise of life humming out there. It’s much too quiet here.’ He died last Friday, aged 55. Since then it’s felt very quiet, both for those who knew him personally, and for the many people who admired his work as a curator and writer. Okwui had a deep, booming voice, and a purposeful one. When he spoke, you listened. It’s hard to imagine not hearing it.

I first met Okwui in 2002 in Kassel, where he was curating Documenta. He grew up in Calabar, a port city in southeastern Nigeria, and was the first non-European to curate the exhibition. He wasn’t grateful for the chance. He knew he’d earned it, which isn’t to say he wasn’t aware of those in the art world who considered him a beneficiary of affirmative action or post-colonial guilt. Tall and dandyish – he loved pointy shoes and ascots – Okwui looked like An Important Man, and was sometimes mistaken for an ambassador in that provincial German city.

In a sense, he was. Okwui was born in 1963, three years after Nigeria won its independence. His formative experience of being an ‘other’, he said, took place not in the West but in Nigeria, when his family, members of the Igbo minority, had to flee their home during the Biafran war. A nostalgic vision of African unity wasn’t an option. Still, Okwui had the old-fashioned aura of the African statesman in the West, and the bearing of an aristocrat. He styled himself as a spokesman for formerly colonised peoples whose images had been distorted or erased from the museums and galleries of the rich world. In his remarkable 2001 exhibition at the Villa Stuck in Munich, The Short Century: Independence and Liberation Movements in Africa 1945-94, Okwui proposed to ‘view the history of the 20th century from the vantage point of the struggle of subject peoples to regain their independence and liberty’.

For Okwui, the museum was a territory to be liberated from the colonial gaze. His first exhibition, In/Sight, a survey of African photographers at the Guggenheim in SoHo in 1996, turned Seydou Keita and Malick Sidibé, among others, into international art celebrities. It encompassed North Africa as well as countries south of the Sahara, and included white, Arab and Asian artists. In his later group shows, notably Documenta, the 2012 Paris Triennale and the 2015 Venice Biennale, he showed up the provincialism of his Western colleagues by foregrounding the work of artists from Africa, Asia, the Middle East and the diasporas of the Black Atlantic.

Okwui’s art world looked more like the world itself. But this was no occasion for self-congratulation, much less for exercises in the sterile American rhetoric of ‘inclusion’, which he disdained. His project was to decolonise the art world: not to make it more ‘diverse’ but to redistribute power inside it.

Art, he believed, like other human activities, took place in a field of argument and struggle over limited resources. He did not shy away from conflict, or from jousting with other curators, such as Robert Storr, with whom he engaged in furious argument over contemporary African art in the pages of Artforum. At the Venice Biennale, he staged a marathon reading of Marx’s Capital. For Okwui, decolonising the art world meant more than having more shows for artists from the Global South: it meant reappraising the entire history of Western modernism from a non-Western perspective. His last published essay was on Andy Warhol’s ‘disaster’ series, including his images of the 1963 civil rights demonstrations in Birmingham, written for the Warhol retrospective at the Whitney.

Okwui’s degree was in political science. He educated himself in the history of visual art, theory and philosophy, and set up a magazine dedicated to African visual arts, Nka, in 1994. However dense his curatorial writing was, it retained the clarity – and the bite – of his background as a critic. He championed a vast range of art, from the expressionist portraiture of Marlene Dumas to John Akomfrah’s immersive films about the post-colonial condition; from El Anatsui’s detritus-based sculptures and Adrian Piper’s fiercely analytic installations about racial identity.

Okwui’s exhibitions were like seminars, packed not only with art but with wall texts, primary sources and documentaries. His catalogues grew to monumental proportions. An unapologetic maximalist, he wasted no opportunity to educate the viewer. He was sometimes accused of being more interested in ideas than in art, of curating ‘CNN exhibitions’. But Okwui had superb taste, with a strong leaning towards an elegant, rigorous formalism. When we first met in Kassel, he rhapsodised over the cerebral, numerically based installations of Hanne Darboven. After being named director of the Haust der Kunst in Munich in 2011, he organised an exhibition of another German pioneer of elegant, rigorous formalism, the music label ECM.

Shortly before the show opened, I witnessed an argument (at a New Year’s Eve party in Brooklyn) between Okwui and Terry Adkins over the respective merits of ECM and Black Saint, an Italian jazz label. Adkins, who played saxophone and made art about black music, claimed that ECM had ‘whitened’ the work of black musicians; Okwui insisted that ECM’s records were better produced and more curatorially inventive. ECM: A Cultural Archaeology, which included a series of concerts by some of the label’s leading musicians, emerged out of Okwui’s reflections on what he called ‘the fate of the black avant-gardes and the paucity of reflection on their giant achievements’. It infuriated him that composers such as John Cage had been ‘institutionally beatified as living embodiments of artistic complexity and genius’, while black musicians of comparable or superior achievement had been forgotten.

The New York minimalist composer, singer and pianist Julius Eastman, for example: a gay black man who had brashly proclaimed his racial and sexual identity in a series of provocatively titled pieces, and died in 1990, just shy of 50. At the Paris Triennale, Okwui helped launch Eastman’s revival by staging a performance of his epic piano works Crazy Nigger and Gay Guerrilla. In an email to me Okwui once described Eastman’s posthumous album Unjust Malaise as a ‘thunderous, melancholic, spiritual and at times funky two hours of music’.

Music seemed to provide Okwui with consolation as his health deteriorated. But he didn’t mellow: his indignation at injustice remained intact, and eloquent, right up to the end. When the artist and writer Hannah Black declared that Dana Schutz’s Open Casket, a painting of the corpse of Emmett Till, should be removed from the 2017 Whitney Biennal and destroyed, Okwui castigated me for criticising Black’s protest as a call for censorship. In his email he dismissed Open Casket (about which I had said nothing; I didn’t think much of it) as a ‘grotesque, sensationalistic and badly painted cheap spectacle’.

‘Did not every avant-garde movement,’ he asked, ‘call for the ransacking of museums, have them emptied and works of art set ablaze atop a funeral pyre?’ A ‘new generation of young global black thinkers and artists’ was emerging, and ‘we should pay careful attention to their rage and anguish.’ He was unmoved by the fact that some prominent black artists had come to Schutz’s defence, saying she had a right to make the painting: ‘artists are complicated characters with hidden agendas and calculations … I read their public declarations with a grain of salt.’ Okwui’s email didn’t change my mind, but it unsettled my sense of what was really at stake.

‘New York seems such a distant memory,’ Okwui wrote to me last July, ‘that I often wonder if I will ever return there.’ He never did, which meant he couldn’t see the Charles White and Bruce Nauman retrospectives at MoMA. ‘I am not sure I am a fan of Bruce Nauman,’ he wrote to me, ‘but I am a great admirer of his relentless difference, his contrarian attitude towards form and material, along with his obsessions with decay, dying, sex, pain, suffering and collapse. He is utterly unique among artists of his stature in his approach to the human condition.’

Okwui’s own view of the human condition darkened considerably in his last year, thanks in part to the political crises in Europe and the United States, especially the recrudescence of overt racism and xenophobia. ‘There is no such thing as a common humanity,’ he said. ‘I believe in simple acts of friendship, constantly reciprocated.’ He was an American citizen, but he remembered what it was like to have ‘the wrong passport from the wrong country in the wrong continent’. He had once been deported from the US to Canada for taking a spring break holiday in Toronto, even though his student visa was up to date. ‘The first thing they try to do to you at the border when you come from a shithole country is to try to steal your humanity, to put you into a process of depersonalisation, to make you feel fear and gratitude for normal courtesy,’ he wrote. ‘Immigration does not stop at the border where Obama and Trump have played politics with the lives of brown people, the true wretched of the earth.’

He was unimpressed by most Western punditry on the ‘the return of the hegemon and its offspring authoritarianism and the rise of the strong man … It’s shocking how few thinkers truly try to place things like migration and the desperation of migrants and their reckless attempt at survival at the centre of policy reflection … We who have families in the developing world already know the cries of the desperate. We are already engulfed by crisis. I read many articles these days about the West, and wonder where is the rest of the world.’

Okwui’s exhibitions raised many questions, but this was never one of them. The rest of the world was always there, front and centre.