The Lille midfielder, already a key performer in Ligue 1 this season, has confirmed his rising potential in Morocco colours.
Bouaddi has started every game since the tournament began and has impressed with his maturity and composure in the biggest matches.
His choice to represent Morocco had been expected for months, following extended dialogue with the Moroccan federation.
Bouaddi's family met with federation officials, national team boss Walid Regragui spoke with him personally, and Mohamed Ouahbi immediately built him into his plans upon taking charge.
France also tracked the situation closely, with Zinedine Zidane personally speaking to Bouaddi in an effort to convince him to commit to Les Bleus.
The midfielder ultimately chose Morocco, a decision that has stirred regret in French football circles.
France's national technical director, Hubert Fournier, addressed the loss in an interview with The Athletic.
"Bouaddi is a talent that we followed for many years. And we know that, in his age category, he is unique. It's a big loss for our federation. But it's his choice," Fournier said.
Fournier explained the reasoning behind France's decision not to select Bouaddi for the World Cup.
"He followed all our selection processes. He spent a year and a half with the Espoirs. He knew he was on the extended list. But we couldn't offer him the opportunity to take part in the World Cup right now. Competition is fierce within the France squad," Fournier said.
He added that head coach Didier Deschamps opted against including Bouaddi before the tournament, with Morocco offering the World Cup chance France could not.
"Deschamps decided not to include Bouaddi and he preferred to play the World Cup with Morocco. The coach felt he wasn't quite ready yet, while Morocco offered him that opportunity. I understand his point of view," Fournier said.
Bouaddi's stock has continued to rise throughout the tournament, with Paris Saint-Germain, Real Madrid, Liverpool, Manchester United, Arsenal and Manchester City all credited with interest in the midfielder.
Lille president Olivier Létang has already made clear the scale of any offer required to prise Bouaddi away.
Speaking to Eurosport, Létang stressed how highly the club rates its academy graduate.
"Plenty of clubs are interested in him, but very few can afford him today. He's already one of the best midfielders in the world and still has huge room to improve. He's only 18 and has his whole future ahead of him," Létang said.
Létang pointed to recent big-money transfers as a guide to Bouaddi's value, citing reported fees for Elliot Anderson (around €135million) and Sandro Tonali (around €115million).
"Look at how much players like that have sold for, players who are much older but without the same room to improve. That gives you an idea of Ayyoub's value, with his unique profile at just 18," Létang said.
Morocco's success in securing Bouaddi looks increasingly like one of the shrewdest pieces of business in this generation of the national team, while France now watch one of their former Espoirs stars shine in different colours.