It's pretty rare for a movie to rise from second place to first at the box office in its second week of release. It's pretty rare for such a movie to defeat a summer smash that's topped the chart for three weeks running. And it's pretty rare for a low-budget, Christian-themed movie with a star-free cast to become the top-grossing film in North America.

And yet, "War Room" did all three of those things this week. After last weekend's impressive $11.4 million debut in the No. 2 slot, the film rose to the top spot this weekend with an estimated $9.4 million from Friday to Sunday (and a projected $12.3 million over the four-day holiday weekend). It dethroned previous three-time champ "Straight Outta Compton" (No. 2, with an estimated $8.9 million from Friday to Sunday and $11.2 million over the Labor Day holiday). It also defeated two new wide releases, one starring the iconic Robert Redford in the nature-travelogue milieu he's best known for, and one installment of a venerable action franchise.

How did "War Room" achieve this surprise victory? The answers have a lot to do with smart timing and marketing, but even more to do with underserved audiences that mainstream Hollywood either ignores or doesn't know how to reach.

It would be easy to dismiss "War Room"'s success as just a matter of good timing. The Labor Day holiday is typically one of the slowest weekends of the year at the multiplex. Plus, "War Room" seemed fortunate in getting to compete against fairly weak rivals.

"A Walk in the Woods," a light comedy-drama starring Redford and Nick Nolte, has a septuagenarian cast and only middling reviews, which can do real damage to the sales for a film whose older target audience still cares what critics think. And "The Transporter Refueled," the fourth "Transporter" thriller, is the first one in seven years and the first without Jason Statham. (Star Ed Skrein is, well, the opposite of a household name.)

Even so, the competition may not have been as weak as it appeared. "Compton" was still strong -- in fact, it was widely expected to four-peat, and it fell behind "War Room" by just $500,000. "Woods" did better than expected, finishing third with an estimated $8.4 million, well above the $5 to $6 million pundits predicted. "Transporter" finished fifth with an estimated $7.13 million, but that figure is just $20,000 below fourth-place finisher "Rogue Nation," so it could rise to fourth by the time the final holiday figures are released on Tuesday.

If "War Room" was fortunate (or shrewd) in its timing, it also benefited from strong marketing and distribution. The $3 million film was produced by the faith-based Affirm label and distributed by TriStar, both arms of major Hollywood studio Sony. The distributor had the savvy -- and the muscle -- to expand from 1,135 theaters last week to 1,526 this week, so it held the inevitable second-week drop in sales to just 18 percent. ("Compton" dropped 33 percent this weekend.)

Meanwhile, "Woods" and "Transporter" were both being handled by indie distributors (Broad Green Pictures and EuropaCorp, respectively) that had never done a wide-release campaign before.

Of course, the main reason "War Room" triumphed wasn't just that it was smartly rolled out onto more than 1,500 screens, but that it was smartly targeted at the right viewers. By now, we should probably stop being surprised when Christian-themed movies become mainstream hits, but the feat is still striking. It helped that Affirm and TriStar knew how to reach a Christian audience through grass-roots marketing and outreach to individual churches.

It also helped that the movie was made by director Alex Kendrick, who turned faith-based films "Facing the Giants,'" "Fireproof," and "Courageous" into modest mainstream hits. So the team behind the film already had the trust of its target audience and experience reaching them through techniques that the mass-market studios are usually too big and lumbering to do well.

But it also helped that "War Room" has a predominantly African-American cast. Tyler Perry has shown how receptive African-American audiences are to Christian-themed movies made within the black community, but Kendrick is a white filmmaker, working in a Christian-filmmaking mini-industry that's no more racially diverse than Hollywood in general.

It's worth noting that this weekend also saw the successful American launch of "Un Gallo con Muchos Huevos" ("A Rooster with Many Eggs"), a CGI-animated feature from Mexico that debuted in the top 10 (at No. 8) with an estimated $3.4 million. That's a very good number for a Spanish-language kids' movie (it earned about the same amount when it opened in Mexico three weeks ago), but it's also not unprecedented. Its distributor is Pantelion, the Spanish-language division of Lionsgate, which has had similar crossover successes at this late-summer/early-fall season in previous years, including last year's biopic "Cantinflas" and 2013's comedy smash "Instructions Not Included," which earned $44.5 million to become the top-grossing Spanish-language film ever released in the United States and Canada.

Like "War Room," "Gallo" offers further proof that there are underserved audiences hungering for movies that respect their cultures, movies that are also universal enough to cross over beyond their target audiences. If the Hollywood studios don't want to leave money on the table, they just have to figure out how to make such movies and how to sell them in campaigns that don't require blanketing the continent with superhero toys and fast-food tie-ins.