But just over a year later, on December 12, 2020, Zam was hanged in Iran, an execution that prompted international condemnation.
How had Zam gone from the relative comfort of his life in France to meeting his death aged just 42 at the hands of the hangman in his home country, whose leaders he had targeted in his work?
His father Mohammad Ali Zam is a cleric still based in Iran and was, at one time, a senior figure in Iranian cultural institutions.
So fervent was his support of the 1979 Islamic Revolution that ousted the Shah that he named his son after its founder, Ruhollah Khomeini.
Colleagues and friends of Ruhollah Zam in France told AFP that he had made the mistake of being lured into a trip to Iraq in October 2019, defying their warnings of danger and falling into a trap set to exploit his own character.
"He played a dangerous game by going to Iraq and he lost," said Mahtab Ghorbani, a Paris-based Iranian writer and a refugee who worked with Zam.
"He was dragged into a dirty psychological game designed by this regime."
'No red line'
Resident in France for almost half a decade, Ruhollah Zam had attracted up to two million followers to his Telegram channel Amadnews, encouraging people to turn out in protests during the winter of 2017-2018 and also publishing sometimes sensational allegations about the Iranian leadership.
As the privileged child of an influential father, Zam enjoyed good contacts in Tehran which he held onto even after leaving the country following the 2009 protests over disputed elections.
He first went to Malaysia and Turkey, and then France.
"When there were turf wars between people in power, they turned to Zam," said Maziyar, a friend and fellow Iranian refugee, who worked on Amadnews and asked that his full name not be published.
"He delivered information without limits, he had no red line, he respected neither the president, nor the supreme leader, nobody. He even laughed at his own father."
But the success of Amadnews and Zam's own growing radicalism proved their undoing as Telegram suspended the account for inciting followers to use Molotov cocktails against police.
Zam's influence appeared to be waning. Even friends began to question if he was pushing too hard for the overthrow of the Iranian regime.
'Alone and isolated'
"Ruhollah became really well known. He advocated the overthrow of the regime and maybe he started to think of himself as a leader," said Hassan Fereshtyan, a Paris-based lawyer who assisted Zam.
"Bit by bit, he lost his friends," he said.
"He was alone and isolated, and part of the Iranian opposition in exile did not trust him," added Ghorbani.
He was also receiving an increasing number of threats, which prompted French police to give him protection.
His friends said this was a dark time for Zam, a hugely ambitious man who feared that the media presence he had built up so fast was now rapidly losing clout.
"He was in the position where he could make bad decisions and fall for the trap," said Maziyar.
In mid-October 2019, he appeared at Fereshtyan's Paris office and told the astonished lawyer that he was going to travel to Iraq to conduct an interview with Ayatollah Ali Sistani, one of the most influential figures in Shia Islam.
'It's the end'
This interview was supposed to launch a new television channel suggested by an individual claiming to be an Iranian businessman.
His associates immediately sensed the danger, given the security influence Iran has in Iraq, a majority Shiite country, following the 2003 US invasion.
"I shouted, I told him: 'If you go, it's the end, you will never come back to France!'" said Fereshtyan.
And even though Zam gave no indication of when he planned to go, he took the plane to Amman and then onwards to Baghdad the next day.
"Everyone advised him against leaving, even his bodyguard, but he simply replied that he was tired of waiting," added Maziyar.
"And he went. Sadly."
Zam telephoned his wife from Amman airport but he appears to have been apprehended as soon as he arrived in Baghdad.
He was later blindfolded, put into a car and driven to the Iranian border in footage later seen on Iranian state TV.
His detention inside Iran saw him in July 2020 give an interview to state TV, a method used on prisoners in Iran that activists regard as a forced confession extracted by torture.
Sitting in a deep armchair, he was interviewed on the programme "Without Compliments" by Ali Rezvani, officially a journalist for state broadcaster IRIB but who campaigners say is actually an interrogator for the Revolutionary Guards.
'Sow panic'
Zam was convicted of charges including "sowing corruption" and spying for foreign intelligence including France and Israel, accusations vehemently denied by him and his supporters.
His execution on December 12 came just four days after the confirmation of the supreme court's verdict was announced, a haste that is unusual.
His father wrote on his Instagram account that he was allowed to meet his son a day before the execution, about which he said Ruhollah had been kept in the dark.
His daughter Niaz wrote on social media that her father had called on WhatsApp -- inexplicably from a +44 UK number -- hours before his execution.
"I knew that was it, and the hardest thing was that I knew and I could not do anything about it!" she wrote.
Still in grief, the family declined requests for interviews from AFP through their lawyer.
The United States and Europe expressed outrage at the execution while UN rights chief Michelle Bachelet said there were "serious concerns" that Zam's capture outside of Iran "could amount to an abduction".
But Iranian President Hassan Rouhani said he did not believe the killing would harm relations between Iran and Europe, noting that capital punishment is part of Iranian law.
And for dissidents based in France, the execution was a warning that their security cannot be guaranteed even while outside the country.
"With this execution, they wanted to send a message to the loyalists of the regime not to take another path," said Ghorbani. "And also to show opponents outside of Iran their power and sow panic among them."
By Stuart Williams and Cecile Feuillatre
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