Krampus defied box-office predictions this weekend when it racked up a far better-than-expected $16 million over its opening frame, beating estimates that had it pegged in the low-teen millions (and in some cases even worse). So how did it defy the odds to become the latest low-budget horror success? Here are five big reasons why. 

1. It capitalized on a dead period for horror movies.

"Victor Frankenstein" is the closest competitor "Krampus" had in the horror realm this weekend -- which isn't much competition at all when you consider that the Daniel Radcliffe-James McAvoy flop fell to 17th place in only its second weekend, with a dismal $253 per-screen average in wide release and a total gross of barely over $5 million. This left "Krampus" as the only real alternative for horror fans this weekend, and it nicely capitalized on that advantage.

2. Audiences liked it, giving the film word-of-mouth momentum.

While a "B-" CinemaScore (based on audience exit polls) may not sound that impressive, it's actually better-than-average for a horror film, indicating that normally critical horror audiences liked it enough to recommend it to their friends. That likely helped boost the film's box-office take throughout the weekend.

3. It had a "Fresh" rating on Rotten Tomatoes.

Rotten Tomatoes has long been the go-to critical aggregator for slightly-more-discerning moviegoers making their weekend movie plans, and "Krampus's" 66% "Fresh" rating -- a better-than-average showing for a horror film -- may have given it the extra boost it needed to appeal to audiences who may have skipped it otherwise.

4. The trailer was great.

The value of a good trailer should never be underestimated, and "Krampus's" promised a fun, unique horror film with a killer monster and instantly-memorable one-liners like Conchata Ferrell's "it looks like Martha Stewart threw up in here."

5. It promised something different.

In a horror marketplace overrun with sequels ("Insidious: Chapter 3" "Sinister 2"), remakes/reboots/reimaginings ("Poltergeist," "Victor Frankenstein") and limp found-footage movies ("Paranormal Activity: The Ghost Dimension," "The Gallows"), "Krampus" offered the taste of something unique -- not to mention an old-school monster of the sort we rarely see anymore. What "Krampus's" success demonstrates more than anything is the continuing hunger for original horror-movie concepts.

A former contributor to sites including MTV's The Backlot and Bloody-Disgusting, Chris Eggertsen worked in film development before indulging his love of pop culture writing full time. He specializes in horror, the intersection of social issues and entertainment and Howard Stern. He's on Twitter @HitFixChris.