This weekend at the box office, the most surprising good news was the unlikely success of Christmas-themed horror comedy "Krampus."

No one expected much from this film. Besides the typically slow weekend, "Krampus" had several strikes against it: no star power, weird genre blend, potentially strong competition with "Hunger Games: Mockingjay -- Part 2" and other popular wide-release holdovers from recent weeks. It was widely expected to open in fourth place, with estimates ranging from $6.5 to $12 million.

Instead, "Krampus" debuted in second place with an estimated $16.0 million, earning an upset victory over holdovers "Creed" and "The Good Dinosaur." So "Krampus" greatly outperformed predictions and, given its reported $15 million budget and $3.3 million overseas gross, is likely to earn a profit by the time its theatrical run ends. By the debased standards of early December, that makes "Krampus" a surprise hit.

How did "Krampus" manage to defy expectations and beat the odds? Here are a few ways:
1. Good Timing
As far as new wide-releases go, "Krampus" had the multiplex to itself this weekend. Plus, it pretty much had the horror niche all to itself. (Its only competition there was last week's dud "Victor Frankenstein," which earned only an estimated $707,000 this weekend, or a paltry $253 per screen.) It's pretty brilliant, actually; conventional wisdom says horror films don't do well in early December, so no one ever releases one at that time, so this year, "Krampus" gets to own an underserved audience. The lesson: (Good) Horror can work at any time of the year.

2. Broad Appeal
Pundits were dismissive of "Krampus" in part because it was expected to play only to younger audiences, who've proved unreliable of late. (Witness the lower-than-expected turnouts for both "Mockingjay" and "Dinosaur" so far.) But exit polling showed that "Krampus" viewers were evenly split among audiences on either side of age 21 and on either side of the gender line. The film's PG-13 rating allowed for kid audiences without making adults think the film was too juvenile.

3. Decent Reviews
"Krampus" actually earned mixed-to-positive reviews, resulting in an aggregate score of 64 percent "Fresh" at Rotten Tomatoes. That's pretty good for a horror film, and it helps explain why older audiences were drawn to the movie. Word-of-mouth, as measured by the film's B- grade at CinemaScore, was also middling-to-good by horror film standards.

4. Surprisingly Weak Competition
The film's broad demographic appeal meant it was competing on the same playing field as "Mockingjay," "Dinosaur," and "Creed." While "Mockingjay" was No. 1 for the third straight weekend, it's still underperforming "Mockingjay -- Part 1" by 12 percent.
Similarly, "Dinosaur" is the weakest-performing Pixar entry in years. Of the holdovers, only "Creed" is outperforming expectations, but the boxing drama is still playing to a predominantly male crowd, while horror audiences tend to skew female, so "Creed" wasn't that big of a threat to "Krampus."

5. Universal's Marketing Comes Through Once Again
Universal had an outstanding spring and summer at the box office before stumbling badly this fall with such films as "Steve Jobs," "Crimson Peak," and "By the Sea."

Still, even with a slate of fall flops, you can't dismiss the marketing team that helped earn the studio one out of every four dollars spent on movie tickets this year. Whatever Universal's marketers did to sell "Krampus" to ticketbuyers (including downplaying the film's comic elements) seems to have worked.
Granted, the extra few million that "Krampus" earned beyond its modest predictions isn't going to be the determining factor of whether or not Universal remains Hollywood's 2015 market leader for the rest of the year. (The upcoming "Star Wars: The Force Awakens" could tip the balance in Disney's favor, though it would have to earn nearly $800 million in North America to do that, which is an awfully tall order.)

Still, this is a sparse season for glad tidings, so Universal will have to settle for the mini-windfall of "Krampus" as an excuse to make merry.