AMC's new TV series, "The Walking Dead," got off to a running start last weekend. Some 5.3 million viewers tuned into the first episode of the zombie-themed horror drama on Halloween Sunday — that's the largest audience for an original series debut on AMC ever, and the top cable premiere of the year in the 18-49 demographic. "It's a good day to be dead," AMC's president, Charlie Collier, said of the numbers. (Watch a trailer for "The Walking Dead.") Just how did the show do so well without a big name cast or a sure-fire commercial formula? Here, five theories:

1. We can all relate to a tale of survival
"With the economy still mired in a four-year slump," and American citizens locked in an ideological civil war, more and more of us are "grappling with basic questions of survival," says Matt Zoller Seitz at Salon. That's the perfect time to release zombie films and television shows. They mirror our own moral dilemmas but in a more "outrageously colorful, and much more exciting" way.

2. It's all down to Halloween... and hype
"'The Walking Dead' had a lot going for it," says Eric Eisenberg at Cinema Blend. "It has been the subject of hype for months, was premiering on Halloween, and received heaps of praise from critics everywhere."

3. People just love the undead
"TV viewers want braaaaaains!" says Melissa Maerz in the Los Angeles Times. Given the public appetite for vampires (see HBO's "True Blood," the CW's "Vampire Diaries," and the Twilight phenomenon), it's unsurprising that a zombie fest would do well. This "undead drama trend is not dying anytime soon." Stay tuned for "the inevitable werewolf soap opera."

4. It's intelligent
"Finally, a horror show on television for people who hate horror," says Mike Ryan in Vanity Fair. Unlike the portrayal of zombies in The Evil Dead or Dawn of the Dead, these undead souls "act exactly like they should: Human beings having some really terrible fever dreams." At its core, "The Walking Dead" is about "human emotion in a dire situation."

5. It's got quality people behind the camera
A tale of "alternate-universe America overcome by flesh-eating zombies" could easily become "lurid, gory pulp," says Scott Meslow in The Atlantic. But "in the hands of executive producer and director Frank Darabont," director of The Shawshank Redemption and The Green Mile, "'The Walking Dead' is as dark and uncompromising as any of AMC's other dramas."