Maybe they found out they were all zombies. That would explain the show's particularly realistic feel. Deadline's Nellie Andreeva says:

The show has six episodes this season, and twice as many next season. It may be more difficult to do twice as many with freelancers, but they're easier to manipulate. A writing staff might get ideas about how they think things should be - hey, let's make the zombies a metaphor for something! - whereas freelancers do as they're told, if they want to work.

I'm only up to episode three, but it's still a fine show. And I'm not a zombie guy. Never had an argument about fast zombies vs. slow, or "classic," zombies. Don't care. I've liked good zombie movies; still recall seeing the original "Night of the Living Dead" in high school, which was the scariest grossest darkest thing in the world at that time. But now the genre is better when parodied; "Shaun of the Dead" and "Zombieland" were better than most of the "Living Dead" retreads. So it's a surprise to see a straight-forward zombie story that works as well as "Walking Dead." Will it be as good next season? Probably. It's too early in the morning to think about these things seriously, anyway. I mean, you probably know where the headline of this entry comes from, but you can't quite figure it out. It'll hit you later. Don't worry. You're not missing much.