Fidelity Investments’s Joel Tillinghast was picking cheap stocks before it was cool.

For most of the past decade, investors have favored big technology companies and other growth stocks over the kinds of overlooked businesses Mr. Tillinghast has spent his career mining.

In the last year, that has changed. An economic recovery, a sharp market rally powered in part by legions of first-time traders, and the meme-stock craze all drew attention to stocks long part of Mr. Tillinghast’s remit. And in a stroke of good fortune, one of Mr. Tillinghast’s longtime holdings, videogame retailer GameStop Inc., emerged earlier this year as one of the hottest stocks of all.

The pandemic led millions to ponder their own mortality—and then trade stocks with abandon. “Having survived it, you had daredevil traders who said ‘You only live once,’” said Mr. Tillinghast, before recounting the phrase’s popular acronym: “Yo. Lo.”

“It was very weird,” he said of the past 17 months.