"Fortnite" is a runaway success for Epic Games. But the free-to-play game may actually be helping the entire industry by expanding the video game market.

First, it begins with its formula for success, which is a combination of its "Battle Royale" mode and the popularity of livestreaming the game via Twitch. The game mode puts 100 players against each other until one person is left standing.

Hundreds of thousands of people watch their favorite Twitch streamers duke it out in "Battle Royale" in real time. Streamers like Tyler "Ninja" Blevins made more than $500,000 a month playing "Fortnite" on Twitch. In March, he even partnered with hip-hop artist Drake, pulling in 628,000 viewers. And in April, "Fortnite" had the longest viewing time on Twitch, totaling 127.9 million hours viewed across more than 10,000 channels.

Gaming studios are jumping into the "Battle Royale" trend, too. Activision is forgoing its single-player campaign to focus on a "Battle Royale" mode for its latest "Call of Duty" game. But it's not just "Fortnite" and its "Battle Royale" that are expanding markets for gaming companies. It's who "Fortnite" is bringing into the video game world.

In a recent report by J.P. Morgan, the investment bank said "Fortnite" is benefiting the gaming industry by expanding its demographics that were normally difficult to tap. "Fortnite" and its "Battle Royale" format have attracted more gamers from younger ages and female players. Gamers playing the game could be in elementary school playing against someone who has already graduated from college.

And according to the same report, the "Fortnite" expansion to other platforms is also welcoming new gamers. When "Fortnite" introduced the version for iOS, it helped introduce gamers, who didn't own a gaming console, into the video game market. It also puts iOS users in a cross-platform "Battle Royale" match against gamers using Xbox, PlayStation and PC.

While "Fortnite" may be a direct competitor to the major gaming companies and their franchises, those companies may need to give a tip of the hat to Epic Games for introducing a new wave of gamers to the video game market.