What was Garth Brooks doing playing a South Jersey line-dance bar on a wintry Monday night?

It certainly wasn’t a case of “how the mighty have fallen.” Brooks doesn’t sell megamillions like he used to, when 1990s albums like No Fences and Fresh Horses moved enough CDs to put him in competition with Elvis Presley and the Beatles for biggest-selling artist of all time.

But Brooks is still a superstar who puts plenty of fannies in the seats, usually at football stadiums or sold-out arena shows. (He played four at the Wells Fargo Center in 2017.) And just last month in Nashville, Brooks won the Country Music Association’s Entertainer of the Year award for the seventh time and third in the last four years, beating out contemporary hit-makers such as Chris Stapleton, Eric Church, Keith Urban, and Carrie Underwood.

So what was the 57-year-old Oklahoman doing, kicking off the post-holiday workweek on Route 38 in Mount Laurel, at Prospectors Grille & Saloon, a 500-capacity club that shares a parking lot with a Walgreens next door?

For starters, he and his six-piece band were enjoying themselves immensely on their “Dive Bar” tour, marrying stadium precision with beer joint enthusiasm while smushed onto a cramped stage whose backdrop promised to deliver “The Best Damn Country in the Whole Tri-State Area.”

It’s safe to say they lived up to that billing.

Playing to a room packed with ready-to-get-rowdy fans who had won tickets through local country station WXTU-FM (92.5), the show began with “All Day Long” from Brooks’ forthcoming album, Fun, a song with beer, a jukebox, and other country tropes in its get-the-party-started arsenal.

Since July, Brooks has been playing occasional minuscule venue shows to promote “Dive Bar,” his hit duet with Blake Shelton that celebrates the down-and-dirty honky-tonk aesthetic of shot and beer joints “that are the safest of the places that a broken heart can hide.”

“Dive Bar” and its double-entendre underwater jokiness (“You’re not the only loved and lost and lonely one who’s ever swum against the tide,” Brooks sang Monday) is more than a blue-collar novelty that consciously recalls his ’90s man-of-the-people hit, “Friends in Low Places.” (That song, the penultimate one of the night, was prefaced by a couple of other hard-to-avoid singalongs: Billy Joel’s “Piano Man” and Don McLean’s “American Pie.”)

“Dive Bar” and its tour — which has the same name as Lady Gaga’s in 2016 — partners with country stations like XTU, which are important allies to Brooks, since he has not let his music be heard on dominant streaming services Spotify and Apple Music. (You can hear him on Amazon Music Unlimited.)

Shows that happen in spaces many times smaller than an artist is capable of playing are not only a thrill for the lucky ticket-holders, they’re also good business, a time-honored strategy for building buzz. And it’s a particularly popular one in the Philadelphia area this week, with Madonna, usually an arena headliner, starting a four-show run at the Met on Saturday.

Brooks’ Burlington County gig was supposed to be one of two on Monday, but his plans to hop on a plane and do a second show in Foxboro, Mass., were nixed by nasty weather.

There’s no telling whether not having to run off and play another show 300 miles away — a rather insane plan even were the weather ideal — made Brooks’ set that much more relaxed. Brooks is such a pro that he probably would have been just as all-in on his performance if he had to play three times on Monday.

But in any case, the energy throughout the 80-minute set was high. And aside from a few overwrought numbers like “That Summer” and “Standing Outside the Fire,” the show leaned in hard on the swinging honky tonk like “Two of a Kind (Workin’ on a Full House)” that’s a Brooks strong point, while not stinting on big hit ballads like the closing tearjerker, “The Dance.”

Always an over-the-top showman, Brooks’ crowd-pleasing persona was in play without the need of stadium-size gestures. He gobbled up some M&Ms given to him by a fan (“I didn’t eat dinner before the show”), signed a man’s detachable prosthetic foot, and threw in a number of covers he used to play when he wasn’t doing dive bars by choice.

Those included the Nitty Gritty Dirt Band’s “Fishin’ in the Dark” and the show’s highlight, a take on George Strait’s “Amarillo by Morning” that paired him with fiddle player Jimmy Mattingly, who, like all the members of Brooks’ veteran band, received a warm and gracious introduction and ovation.

Remembering performing “Amarillo” back when he was an unknown enamored of Strait, Brooks said, “This all started in a place called Willie’s Saloon in Stillwater, Okla., just wanting to be someone else.”

Later, he thanked the crowd for sticking with him once he became Garth Brooks and “for remembering my music, and treating it with so much respect.”