There's no doubt about it: the X-Files' premiere ratings were huge. Just how huge? Taking into account "three-day delayed viewing" numbers, the first episode of the revival was watched by 20.3 million over that period, and 21.4 million when taking into account those who watched it on Hulu and the Fox Now app. Those are big, big numbers in today's fractured TV landscape, and on a par with the season premieres of X-Files' third and fourth seasons during the series' heyday. So how did FOX manage to turn the 13-year-old show into a ratings hit? Here are four big reasons.

1. It effectively tapped into nostalgia for the old series.

The X-Files' pop-cultural influence in the '90s can't be underestimated: the show was a huge phenomenon during the majority of its original run, and FOX very effectively capitalized on burning nostalgia for the old series by trumping up the "reunion" aspect between Mulder and Scully in the marketing materials for the new episodes.

2. It was marketed as a true "event," lending the revival a must-watch aura.

Getting David Duchovny and Gillian Anderson back for only six episodes could have certainly been spun as a disappointment by fans pining for their return (though truth be told, the limited commitment was what sold both stars on the new episodes in the first place), but FOX smartly marketed the limited run as an "event." This lent a "must-watch" quality to the new episodes, a particularly important hook for new viewers who may not have been familiar with (or even been alive during) the show's original run.

3. Anderson and Duchovny were out everywhere promoting this thing.

Whatever FOX paid their stars to return (and shame on them for initially offering Anderson only half of what they agreed to pay Duchovny), it was more than worth the investment. Both actors went all in on the show's promotional blitz, gamely appearing together on multiple late-night talk shows and even capitalizing on their famed sexual tension in a sketch on Jimmy Kimmel Live. You couldn't escape the promotional blitz here, and Anderson and Duchovny contributed mightily to that effort.

4. The old episodes have been readily available for bingeing on Netflix.

Having easy access to streams of old TV shows has arguably led to any number of revivals of beloved properties, and The X-Files is no different: all nine previous seasons have been available to binge on Netflix on-and-off for years, breeding a whole new universe of young fans and reminding old fans why they loved the show in the first place.

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.