Matthew eventually worked his way up to the top 1% of players who compete world-wide at Tencent Holdings Ltd.’s popular fantasy game “League of Legends,” which boasts 100 million monthly active users. The 21-year-old bought a Toyota 86 sports car last year with his earnings.

“He makes more than me,” said Mr. Higginbotham, a certified public accountant, “and here I’ve been in the workforce for 40 years.”

Mr. Higginbotham has since seen the light. He started recognizing similarities between the game’s battle tactics and his own experience in the U.S. Army. “It’s virtual warfare,” he said.