Boris Johnson arrived at the Vote Leave headquarters the morning after the EU referendum hugging staff and “punching the air like Maradona after a great goal”, according to the man who led the winning campaign.

Dominic Cummings, a former adviser to Michael Gove who was appointed campaign director for the leave side, said it was nonsense that Johnson and Gove did not expect to triumph and were consequently regretful.

The pair seemed subdued at a press conference the day after the referendum as they liked David Cameron and “did not want to be seen as dancing on his grave”, Cummings wrote in a long post about the campaign on his personal blog.

“Some of the media created the psychologically compelling story that they were regretful/frightened about victory, but this was not at all their mood in HQ on the morning of 24 June,” he wrote. “Boris came in punching the air like Maradona after a great goal, hugging staff and clearly euphoric. It is completely wrong to portray him as regretful.”

The piece by Cummings, which runs to just under 20,000 words, credits the involvement of Gove and particularly Johnson for the leave victory, saying the vote would likely have gone the other way without the support of both.

Cummings said Gove was vital in honing Vote Leave’s message, and without Johnson, Nigel Farage “would have been a much more prominent face on TV during the crucial final weeks” – potentially scaring off middle-class support.

Cummings also said the hugely controversial pledge that leaving the EU would free up £350m a week to spend on the NHS was vital to swinging the referendum, as was the message on reducing immigration.

“Would we have won without immigration? No. Would we have won without £350m/NHS? All our research and the close result strongly suggests no,” he wrote.

Facebook Twitter Pinterest Cummings takes aim at Ukip and Westminster lobby correspondents in his near-20,000 word blogpost. Photograph: parliamentlive.tv

Cummings also claimed that the NHS pledge, which he says was specifically to spend £100m more a week on health, was serious and would have been kept by Johnson or Gove, had either become prime minister.

However, the main thrust of Cummings’ wide-ranging and occasionally rambling thoughts – at one point he spends several paragraphs comparing Robert Peston and other pundits to a character from Anna Karenina – is to emphasise the complex reasons for the leave victory.

The post dismisses the idea that the Brexit vote was caused by an unstoppable tide of populist feeling, saying if only one of a series of very variable circumstances had gone differently, the result would have changed. Cummings wrote:

Leave won because 1) three big forces [the immigration crisis, the financial crisis and the euro crisis] created conditions in which the contest was competitive 2) Vote Leave exploited the situation imperfectly but effectively 3) Cameron/Osborne made big mistakes. If just one of these had been different, it is very likely in [remain] would have won. Overall, the now-mocked conventional wisdom that ‘the status quo almost always wins in referendums like this’ obviously has a lot of truth to it and it only proved false this time because of a combination of events that was improbable.

One advantage handed to Vote Leave, Cummings said, was a media “obsessed with process and the snakes and ladders of careers”, which thus heavily covered the involvement of Johnson and Gove.

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“We could not match No 10 in the golden currency of ‘names’,” he wrote. “But we could give the media an even more valuable currency – a leadership story.

“The media were understandably obsessed with this story, so we served it up to them in such a way that they also had to cover our message. For 10 days, we dominated the news with a set of stories on the Australian points system, VAT on fuel, Turkey, the NHS and so on, all based on ‘it’s safer to take back control’.”

As is perhaps expected for a man known for his rudeness while working for Gove, Cummings is blunt about his opponents and allies, and admits he is “not motivated by people in SW1 [Westminster] liking me”.

Addressing the charge that he dislikes David Cameron, with whom he had previously fallen out, Cummings wrote:

Wrong. I do not hate Cameron. I do not respect him, which is different. I thought that he was in politics for bad reasons – essentially because he was someone who wanted ‘to be’, not someone who wanted ‘to do’ ... and his priority was himself and a small gang, not the public. I also thought Cameron was mostly (not all) bad at the job, despite having some of the necessary temperamental characteristics, and was flattered by having Brown then Miliband as opponents.

Cummings described the most important part of his role in the campaign as “trying to suppress/divert/overcome internal coalition warfare to a level where about 10 crucial people were protected enough to do their jobs”.

He reserved some of his heaviest fire for the media, saying most political correspondents and commentators should be fired, and for Ukip, who were involved in the unofficial Leave.EU campaign.

Cummings wrote: