There was a time when a Top 40 station played all the hits, regardless of genre. We’d hear Motown and the Merseybeat and the man from Memphis back-to-back-to-back, and if you’re under 40 years old you have no idea what I mean. Radio, both AM and FM, eventually fragmented. Pop goes here, hip-hop there, classic rock over there. Where once there was an audience for all, there’s now an audience for each.

If you’re wondering why Arthur Blank’s MLS team, the official announcement of which came Wednesday not far from where the billionaire’s new stadium will stand, can make it in a city where other sports ventures have failed, think of radio. In the olden days before cable TV and the Internet, we all pretty much liked the same things because niches were hard to find. Today’s world is one where niches can be located and frequented at the touch of a key.

For us in the USA, soccer might not be for everybody. The USA, however, has become a place where nothing has to be for everybody. The Seattle Seahawks just won the Super Bowl. The Seattle Sounders are the MLS’ most successful franchise. The teams play in the same stadium. According to Blank, who also owns the Falcons, only 3 percent of Seahawks fans buy tickets to Sounders games.

Said Blank, speaking before Wednesday’s announcement: “We feel very differently (about the MLS) than we might have felt 10 years ago.”

Said MLS commissioner Don Garber: “This country has changed in the past 10 years.”

He ticked off reasons: The change in demographics, the surge in the Hispanic population and the exposure in the U.S. to global soccer via TV. What was a nondescript soccer league for the first decade of its existence has become one of the 10 best — Garber said his league ranks seventh, which surprised Blank — in the world. Ten years ago, the market for soccer in this country was slender. As the nation changes, the market grows.

Hispanics comprise 33 percent of the MLS audience. (Not incidentally, The Home Depot — another company about which Blank knows a bit — was among the first major businesses to market itself heavily to Hispanics.) In a Luker poll for ESPN, pro soccer ran third behind the NFL and a tick behind the NBA among those 18 through 34 — that’s the millennial generation, or Gen-Y — who were asked to identify their favorite sport. College football was fourth, major league baseball fifth.

“Our formula is for a downtown stadium,” Garber said, and that flies in the face of what we thought we knew about soccer and its appeal. The term “soccer mom” became a buzz phrase for suburbia, for years it was believed that if the sport was going to become more than an afterthought in these United States, it would be because the kids who strapped on shin guards for weekend matches would pester their soccer moms and dads to take them to an MLS game. That never quite worked.

But the millennials who grew into discerning consumers, who discovered the sport either by playing or watching, have made their own demographic noise. These are the people — generalizing here — who work downtown, who hold high-tech jobs and who aren’t afraid to embrace the sport that doesn’t let you use your hands. Along with the Hispanic constituency, Gen-Y is the MLS target audience, which is different from the folks courted by Blank’s Falcons or the NBA Hawks or the suburbanites who triggered the Braves’ move to Cobb County.

The direction in which this nation is headed is the wind at MLS’ corporate back. There’s cold logic in this, but there’s also the fire of zealotry. Soccer fans worldwide tend not to be casual observers. They wear the scarves and sing their songs and brandish their flags with a passion not seen in any other team sport. That’s why so many of them made the trek downtown Wednesday for the announcement of a team that won’t begin play until 2017.

“We would try (to sell the MLS) to everybody in Atlanta and the state of Georgia,” Blank said, but that’s never going to happen. Aging Baby Boomers won’t suddenly decide to burn disposable income on the sport they’ve spent their lives ignoring. Soccer can never be as big as American football. But soccer can fill a need in the lives of enough Americans — and enough Atlantans — to find itself a lasting place in the city that, in terms of sports, ranks among the quirkiest.

Put it this way: Blank’s teenage son Josh has grown up around an NFL franchise, but what sport does he play and watch incessantly on TV? The other football.