Mr. Lupo says he rose to the top of the crowded, highly competitive live-gaming pile through luck. Five years ago, he was an information technology specialist at an insurance company and started live streaming part time on a game called Destiny. At first, eight people watched, but the audience grew quickly. Mr. Lupo has top-notch skills, the warm, authoritative voice of a drive-time radio D.J. and a gift for wry wit, even when mortally wounded.

“Why would I need to practice?” he asked viewers, after losing that Call of Duty game. “I’m a god. I’m insane. Look at my body, dude.”

What truly launched Mr. Lupo was a perfectly tossed virtual grenade. He lobbed it at Mr. Blevins while the two faced off in a first-person shooter called PUBG. A video of the encounter shows a stupefied look on Mr. Blevins’s face, displayed in a corner of the screen, which gradually segues into laughter and delight, as the death of his avatar sinks in.

“We hit it off immediately,” said Mr. Lupo. “We were like brothers, and people liked watching that friendship grow.”

Around this time, Fortnite made its debut and became a cultural phenomenon. Mr. Lupo and Mr. Blevins started teaming up to play against others. (Each game starts with 100 players). Mr. Blevins later asked Mr. Lupo to serve as a play-by-play commentator during a Fortnite event at the Luxor Resort and Casino in Vegas.

“About 300,000 people watched live,” Mr. Lupo said. “And a couple million more watched later.”

Mr. Lupo spends each day with an overhead camera pointed at his hands, another camera pointed at the side of his face and a display of what he sees on the screen. Most of the time, he controls an avatar who is both running for his life and in the midst of a frantic killing spree. He and his online teammates — he usually has a few, whom he talks to through a headset — scramble at breakneck speed, defusing bombs, sniping at enemies and hurtling over landscapes in hijacked trucks. It seems the opposite of relaxing.