That "Deadpool" opened No. 1 at the box office this weekend isn't a shocker. Analysts expected it to debut with around $65 million. They were off by, you know, only about $70 million.

According to estimates, the snarky, sword-happy superhero actually brought in $135.0 million from Friday to Sunday -- with a likely $150 million haul by the end of the four-day President's Day weekend.

In addition to having the biggest opening weekend ever for an R-rated movie, and R-rated comic book movie (sorry, "300" and your puny $70.8 million), "Deadpool's" debut smashed all kinds of records. It's the biggest February debut weekend ever (beating the $85.1 million earned a year ago by "Fifty Shades of Grey"). It's the biggest winter-season opening ever (ahead of last winter's "American Sniper," which went wide with $89.2 million in January 2015). And it's the biggest debut ever for 20th Century Fox (beating 2005's "Star Wars: Episode III -- Revenge of the Sith," at $108.4 million).

So how did predictors miss the mark by more than half? Here are some possible reasons why "Deadpool" did better than anyone anticipated.

1. An Epidemic of Underestimation
Truth is, the pundits have been off their game for at least a year when it comes to surprise blockbusters. They lowballed predictions for such 2015 hits as "San Andreas," "Pitch Perfect 2," and "Straight Outta Compton." They were off by about $80 million for "Jurassic World," which broke the record for biggest opening weekend of all time, until "Star Wars: The Force Awakens" opened even bigger six months later.

Why are the experts so far off? In some cases (especially "Pitch Perfect 2" and "Compton"), they ignored the hunger felt by largely underserved audiences to have a movie that didn't just appeal to them but even represented them. In some cases, the movies surprised analysts by succeeding during what are traditionally not peak moviegoing seasons.

Certainly, February is usually a fallow month for moviegoing. Plus, "Deadpool" had a hard R rating, a leading man with a mixed track record at best, and no 3D surcharges. Opening on Valentine's Day weekend, "Deadpool" didn't exactly seem like an ideal date movie. So there are several reasons why experts expected the movie to do only half as well as it did. Nonetheless, "Deadpool" managed to turn many of these weaknesses into strengths. For instance...

2. R-rated Comic Book Movies are Still a Novelty
To date, there have been only a handful, most of them based on less-than-mainstream titles such as "300," "Kick-Ass," "Kingsman: The Secret Service," (above) and "2 Guns." Only a few have come from well-known comic series or graphic novels, like "The Punisher," "Watchmen" and the "Blade" trilogy. "Deadpool" stepped into an empty arena full of creative possibilities, and curious audiences flocked to see how the filmmakers might exploit those freedoms. Here's hoping more studios take a risk on whatever R-rated Marvel or DC properties whose rights they hold.

3. Ryan Reynolds
The former Green Lantern is generally considered talented, charming, and handsome, but he's never been a big box office draw. Most of his movies that opened well have done so with either Reynolds appearing in a rom-com, or playing second or third banana to a bigger star.

His biggest opening to date in a movie he carried himself was "Green Lantern," which enjoyed a so-so $53.2 million debut on its way to becoming one of the biggest flops in recent memory (the 2011 film cost a reported $200 million and earned back just $116.6 million in North America). So it's no surprise that analysts were wary of how he'd fare carrying another superhero movie.

Still, Reynolds is golden when he finds a movie that suits his raised-eyebrow sense of humor. Audiences seem to know this, and they turned out to see Reynolds be Reynolds.

4. Strong Reviews
To attract the older audience it needs, it helps if an R-rated movie wins over the critics. "Deadpool" did, scoring an 82 percent rating at Rotten Tomatoes and 65 percent at Metacritic. "Deadpool" also earned an A from audiences at CinemaScore, indicating very strong word-of-mouth recommendations from viewers, both men and women.

5. Weak Competition
This weekend's other two new wide releases, "How to Be Single" and "Zoolander No. 2," were both supposed to open around $20 million. Yet "Single" pulled in just an estimated $18.8 million, while "Zoolander" picked up just an estimated $15.7 million -- slightly more than the original film opened with 15 years ago. Reviews for "Single" were middling, while those for "Zoolander" were scathingly awful. Advantage: "Deadpool."

6. Valentine's Day Falling on a Sunday
That's an accident of timing that's easily overlooked. But if it had fallen on a Friday, the romantic comedy "Single" would have made for a stronger date movie than it did with Valentine's Day coming at the end of the weekend. That also helped "Deadpool," which didn't have to worry about losing the couples audience on Friday night.

7. Fox's On-point Marketing
Fox seems to have been teasing this movie for at least a year, with red-band trailers that played up the movie's humor, violence, and raunch. The message -- this is not your grandmother's superhero movie, unless your grandmother is Betty White -- came through loud and clear. Of course, the saturation marketing wouldn't have worked so well if critics and audiences didn't feel that "Deadpool" delivered on the hype.