Plainly, these matches are not for footballers of junior years. Mbappe, though, leaves Moscow with four tournament goals, the Russia 2018 award for best young player and immortality back in France. The sport, the industry opens up before him, from his base at Paris Saint-Germain, from where every top European club would love to extricate him.
The French player he most resembles, Thierry Henry, was 21 when France won their first world title in 1998, with Stephan Guivarc'h and Youri Djorkaeff up front and Zinedine Zidane pulling every string. Mbappe was born six months after that triumph, and now Paris rejoices again to see a multicultural team bestride the world with a superstar at its heart.
"I was told that the country was in madness, that Zidane had scored twice in the final against the great Brazil," Mbappe told Le Monde. "When you go to the youth teams in Clairefontaine [France's academy], you don't know that period, but you get the impression you were there because they were so influential."
Mbappe scored France's fourth goal of a rollercoaster game with refereeing controversies, familiar Croatian fightbacks and vindication for Didier Deschamps, the France coach, who switched to a more conservative plan in the first group game against Australia and stuck with it all the way to the final. Mbappe's goal was fired from outside the penalty box past a goalkeeper, Danjiel Subasic, whose performance fell apart after half-time.
Pragmatism might have smothered France's spirit, but Deschamps managed to see them over the line in large part because Mbappe was there to torment defences with his speed, his joie de vivre. A stunning performance against Argentina was his coming of age as an international footballer. His team-mates nicknamed him '37' after he clocked 37kmh (23mph). Croatia defended mightily here but were spun on their heels every time the ball was sprayed to Mbappe in his wide-right position. Too good to be just a winger, he is nevertheless devastating out on the touchline: the one French weapon Croatia could do nothing about. Olivier Giroud on the other hand went 546 minutes in Russia without a shot. His day even included a high-five for a Pussy Riot pitch invader.
Mbappe is an extraordinary young man, and not just for the pace and effervescence of his attacks. In the Le Monde interview, he spoke with the wisdom of one who has spent many years reflecting on their career from a vineyard. "For me, football is more than a sport, just look at the impact it has on society," he said. "People come to the stadium to forget their lives for 90 minutes, and it's up to us to give them satisfaction; to get them out of their chairs and to fall asleep with stars in their eyes. When I was younger, there were players who gave me pleasure, and now I'm in that role."
When he said this, winning the World Cup was a distant hope, complicated by a fear that this crop of French players were falling short under Deschamps. Some from the 1998 generation wondered whether this lot lacked the mental toughness to win a tournament. Mbappe walked into Russia as the next big hope but without the seniority to influence policy. Deschamps said he had delivered tough messages to his young player but observed that Mbappe was "a clever man" who "knows how to listen" and "knows what he wants."
Mbappe himself told Le Monde: "It's the pleasure of the game, to score, to make the teammate shine. When you do what you love, you don't want to be a transient: you haven't sacrificed your whole life to be an extra; I hope to leave my mark on football."
It was a prescient conversation. "It's something extraordinary to say to yourself that the happiness of all French people is in your hands," Mbappe said.
Unusually, for a prodigy, he seems aware of his own role in the drama, the wider story of football and how it affects the world. He has that filmic sense of his own talent.
But there will be downsides and temptations. "I can't be Mr Everybody anymore," Mbappe said. "For example, you're at home, bored, going out for a walk for ice cream. It's over. I wouldn't even have time to lick it before there would be 500 people around my ice cream."
If anyone can handle becoming a legend, Mbappe can. Two decades after France's first World Cup, along came a second, inspired by a lad born inside that 20-year cycle with a fresh sheen of brilliance.
