The fight is due to be held in Diriyah, on the outskirts of Riyadh, on December 7.
“We had approaches from Saudi Arabia, Dubai, Qatar and Abu Dhabi,” Hearn told a media conference in London, explaining the decision to stage the fight In Riyadh.
“We wanted to go somewhere that believed in the sport of boxing, which had a vision. We already knew Saudi Arabia was for real and knew they were investing in the sport of boxing. That was very important for us.”
“It’s likely to be yet another opportunity for the Saudi authorities to try to ‘sportswash’ their severely tarnished image,” said Felix Jakens, Amnesty International UK’s Head of Campaigns.
Hearn also believes the country’s growing population — over 34 million — can give boxing a platform to reach new levels of popularity.
“If Saudi Arabia is going to invest in these fights, with the population they have, with the potential to grow the sport of boxing, you could be seeing a big change in the dynamics of the sport, which truly excites me,” Hearn added.
CNN has reached out to Saudi Arabian government officials but has yet to receive a reply.
On Wednesday, a video on social media appeared to show Ruiz Jr. dismissing the fight would be held in Saudi Arabia and a widely reported television appearance later added to the confusion.
“I have not signed anything yet, we are negotiating everything,” he told ESPN in Mexico, before stating he would prefer the rematch to take place in New York.
However, Hearn said that both fighters have signed the contract and confirmed the fight would go ahead.
Ruiz, who was born in California but has Mexican parents, had made calls for the rematch to be held in Tijuana where he made his professional debut in 2009.
The Principality Stadium in Wales — the site of two professional victories for Joshua — had previously been thought of as the most likely site for the fight.
“Ruiz had a moan about the UK,” added Hearn. “We said: there’s your neutral venue.”