"History will record that nobody was more responsible for Donald Trump being in the White House than this woman (Gwen Stefani)," he claims in the new film, Fahrenheit 11/9, which looks at how the billionaire reality star reached the pinnacle of US politics.
He claims Mr Trump cooked up a "fake announcement" when he found out NBC was paying Stefani more to join The Voice than he was getting as the star of The Apprentice.
"He paid a bunch of extras $50 a piece to be his cheering supporters," said Mr Moore. "He would prove to NBC that he was more popular than Gwen Stefani and then they would give him more money.
"He would also show them how good he was at improv with his fake presidential announcement and that's when things went off the rails."
After calling some Mexicans "rapists, criminals and drug dealers" in a bizarre rant during the event, he was dumped by NBC.
The plan backfired and he was out of a job.
"Though he had no real plans to run for president, his sons encouraged him to go ahead with the two rallies that he had booked and paid for," said Mr Moore.
It was there the veteran reporter claims the billionaire had his "epiphany" when he looked out over a sea of people who supported his ideas.
From there, the film, looks at how these two rallies spiralled into a movement which would see Mr Trump ascend all the way to the White House.
Mr Moore takes aim at the way the media used the reality TV star's rallies for ratings and the broken system which allowed Hillary Clinton to be the favoured Democrats' choice over Bernie Sanders.
Taking major shots at Ms Clinton, as well as her husband and Barack Obama's legacies, which he claims have created a feeling of apathy among millions of Americans, he also takes aim at himself.
The film shows a clip of himself with The Donald on a daytime TV interview and Mr Moore, bemoans how he could have asked hard questions but instead just made a joke about unemployment.
He too, it appears, had been sucked in by the Trump effect.
However, the majority of the film actually focuses on how Mr Moore's Democrat heartland home state of Michigan had ended up voting for the Republican showman.
In particular he looks at the city of Flint, where the water supply had been switched by Republican Michigan Governor Rick Snyder, leading to "an entire city being poisoned."
He speaks to families who lost loved ones to a sudden and unprecedented outbreak of legionnaires' disease β which has been attributed to lead found in the city's filthy water.
In typical Michael Moore fashion, he takes matters into his own hands by walking into Mr Snyder's office building with a pair of handcuffs to "arrest" the governor for "intentionally poisoning the people of Flint".
However, the film is not just a depressing tear-jerker about a poisoned city and a broken political system.
Mr Moore claims the USA is actually way more liberal and forward-thinking than people give it credit for β citing statistics on gun control, healthcare and better pay that seem at odds with what the political establishment votes for.
He follows the everyday Americans fighting for these causes and the challenges they face.
