Even the network behind “Hatfields & McCoys” was shocked it made History.The morning after the premiere of the historically based miniseries, network topper Nancy Dubuc received an email containing early ratings info. “It came with an expletive that you can’t print in the subject line,” she remembers with a laugh, “and said, ‘Hold onto your hats. There’s something going on here.’ ” Indeed. By the time the miniseries starring Kevin Costner and Bill Paxton as the patriarchs of the famously feuding families had wrapped its three-night, six-hour run over Memorial Day weekend, it had become an unlikely success story, shattering ratings records with an average of 13.8 million total viewers — enough to make it the second most-watched entertainment program ever on basic cable. Another reason to celebrate came in July, when “Hatfields” received a network-record 16 Emmy nominations, including nods for miniseries/movie and lead actor recognition for both Costner and Paxton. Not bad for a network making its official debut in the scripted arena (particularly given that its first attempt, 2011′s “The Kennedys,” was abandoned amid controversy and ultimately aired on ReelzChannel). “I don’t think anybody thought ‘Hatfields & McCoys’ was going to be in vogue,” says Costner, who played Devil Anse Hatfield and also signed on as a producer.”That it kind of blew up was great. We worked very hard at trying to get it just right.” For exec producer Leslie Greif, its staggering success felt like vindication after being rejected by numerous other networks. Greif says he’d tried to get the miniseries made for nearly 30 years, long enough to have had discussions with both Burt Lancaster and Burt Reynolds. “I heard ‘no’ for so many reasons,” says Greif, who listed several excuses for why the project wouldn’t work. “It’s a period piece. The script’s too complicated. Nobody knows the Hatfields and McCoys, it’s just an expression.” Ironically, the miniseries may have succeeded partly because of those very factors. “It broke all the conventional rules of the moment,” says TV Guide senior critic Matt Roush. “This kind of epic historical miniseries isn’t being done anymore, but there’s obviously an appetite for it. (Especially when) you have a story that’s iconic but hasn’t been done to death.” The draw of seeing Costner in a genre he’s already proven popular — look no further than the Oscar-winning “Dances With Wolves” — was also integral, says Roush: “Having a star like Kevin Costner gave it a sense of being an event. It’s the kind of thing you’d normally see on HBO.” “I said, ‘You have to trust this material,’ ” says Costner of his insistence that the entire script be shot. He firmly believed that, to paraphrase a line from another of his hit films, if you build it as written, they will come. “Nancy Dubuc was a real good partner. She understood that it was important to have a complete picture of what happened (between the families). If something’s really interesting, I never think it’s too long.” Feeling they were on to something special, Dubuc and her team worked overtime to build awareness, employing creative marketing ploys (including covering New York City subway cars in “Hatfields & McCoys” images) and engaging in clever on-channel promotion. Another pivotal part of the equation was timing. Memorial Day weekend is generally considered a quiet time for TV, but History execs were confident it was ideal for the net’s male-skewing audience. “Leading up to it, there are key sporting events” — including the NBA and NHL playoffs — “where we could focus some of our media muscle,” Dubuc says. “We never really saw (the holiday weekend) as a risk.” Now no one else seems to consider projects about the clashing clans a risk, either. NBC has a pilot produced by Charlize Theron in development, and there are reports of a reality series starring descendents of the original families. History, though, is moving into the future with its next scripted project, “Vikings.” “As long as everyone else keeps copying and we keep leading, I think we’ll be in good shape,” Dubuc says.