In the UN general assembly chamber, the world’s leaders gathered to share the latest grim news of the planet’s climate crisis, but 100 metres away another meeting had been prepared: a summit of one.

Donald Trump had booked a separate venue in the middle of the UN climate action summit, to hold his “global call to protect religious freedom” – an issue close to the heart of the core supporters whose turnout will be critical in next year’s presidential election.

The 10 long rows of desks at the back of conference room 3, usually assigned to member state delegations, had been made available to representatives of American religious groups who had been issued tickets for the occasion.

As the room filled up, there was growing anticipation of Trump’s arrival. Delegates were asked to take their seats three times – only for the alert to be lifted and the crowd permitted to relax. It turned out the president had made a last-minute change to his timetable, and paid a visit to the climate change summit after all.

On Sunday, Trump had seemed taken aback when asked whether he was snubbing the world and its concerns about the climate emergency.

“No, it’s not a snub at all. I’m very busy,” he said, mentioning he had been briefed on floods in Texas. “The floods are very important to me, and, uh, climate change – everything is very important.”

Trump’s surprise appearance at the climate summit coincided with a speech by the Indian prime minister, Narendra Modi. As the Indian leader spoke, Trump leaned forward in his seat as if listening intently – but it was unclear if was wearing any form of device to hear the translation.

He stayed to hear Angela Merkel, but left when it was the turn of the Chilean president, Sebastián Piñera. He completely missed Greta Thunberg’s accusation that the world’s leaders “are failing us”.

His arrival at the religious freedom meeting was heralded by a scratchy recording of trumpets, possibly playing Hail to the Chief, and he walked in accompanied by the UN secretary general, António Guterres, his secretary of state, Mike Pompeo, and his new ambassador to the UN, Kelly Craft.

They took their positions on the speaker’s dais, and a silence quickly descended. And it continued. For about a minute. Trump drummed his fingers together. It eventually became apparent that no one was sure who would speak first.

In the end, it was Craft who took the plunge. Either she had forgotten she was supposed to be the host or she had been supposed to have been introduced by somebody else who had failed to show up.

She quickly recovered her momentum, however, demonstrating the qualities, apart from being a major Republican donor, had appealed to the president when he picked a foreign policy neophyte to represent the US at the cockpit of the international community.

Her speech was a paean to Trump.

Amid “the chill of a world that seems increasingly disinterested in defending the rights of all people to exercise their sincerely held religious beliefs” the ambassador said a new champion had emerged.

“Under his guidance, the state department has become a watchful defender of religious liberties,” she said. Trump had, after all, chosen Mike Pence, who Craft said was “an unpretentious man, who not only believes in the power of religion. He lives his religion.”

The ascendancy of this committed evangelical Christian to the No 2 spot was itself “a first-class demonstration of President Trump’s wisdom in selecting those who serve him closest”.

Trump’s introduction drew a standing ovation from the crowd.

Trump generally stuck to his prepared text about religious persecution, with ad libs, only to express his disbelief that he was the first US president to come to the UN to speak up for religious liberty.

He ended with an appeal to all governments “to honour the eternal right of every person to follow their conscience, live by their faith, and give glory to God”, and then handed over to Guterres.

By this time, Guterres, having been obliged to leave the climate summit he had spent a year planning to find himself in the midst of a political rally, was leaning as far away from Trump as his seat would allow.

The secretary general listed his own efforts on behalf of freedom of faith and talked about the hotspots around the world where that freedom is under threat.

But here was another way in his Guterres’s speech resembled Trump’s. In their litany, neither man mentioned China, which is currently detaining more than a million Uighur Muslims.

As the Trump administration has put less emphasis on the UN, Chinese influence has flourished. Beijing had not sent a representative to conference room 3, but its presence was keenly felt.