Giorgio Calandrelli, 26, used to play the game Fortnite solely for "fun." That was until his debut competition under a major esports brand last year.

The Italian professional gamer, who is known to his fans as "Pow3r," says he faced numerous setbacks in his opening bid to impress his new team, London-based Fnatic.

"I f**ked up," he says with candor. An accidental misclick that pulled him out of his game also cost him a match. "The tournament is about consistency and getting the most kills as possible to get in the top 20," Calandrelli told CNBC. Each move he makes matters.

Luckily for Calandrelli, he was afforded a comeback, accruing 20 online kills in a "special challenge" game that won him a lucrative $10,000 prize. Altogether, Fnatic's Fortnite team managed to bag more than $100,000 over the course of the tournament.

And that's just the tip of a growing iceberg. Fnatic says that prize pools in the first year of a Fortnite competition have ranged from $1 million to $20 million. Last year, the game's developer Epic Games announced it was committing $100 million for Fortnite tournament prize pools from 2018 to 2019.

But while esports has grown up as an industry over the past decade, in terms of both money and viewership, its stars — and fans — seem to be getting younger and younger.

Last month saw 16-year-old gamer Kyle "Bugha" Giersdorf haul a huge $3 million reward after coming first place in the Fortnite World Cup, the championship dedicated to the popular battle royale game.

Fortnite has helped reignite interest in esports, with titans of the entertainment industry struggling to figure out how to catch up. Comcast, for example, recently announced it would build a $50 million arena designed to accommodate esports tournaments.