The Walking Dead regularly scares up monster ratings for AMC. Last year's MTV Video Music Awards was the highest rated ever. But neither measures up to the History channel miniseries, Hatfield & McCoys, which just became the second most-watched entertainment program in the history of basic cable television. (Only the Disney channel's 2007 TV movie High School Musical 2 ranks higher.) The three-part miniseries, starring Kevin Costner and Bill Paxton as the patriarchs of the famous feuding families, was History's first foray into scripted programming. The trio of episodes now occupy three of the top four most-watched slots for entertainment shows on cable, led by the finale, which drew 14.3 million viewers. Why was Hatfields & McCoys so popular? Here, four theories:

1. It appealed to older viewers
The key to this ratings win: "Lots and lots of older viewers," says Josef Adalian at New York. Roughly 60 percent of the series' audience qualified for an AARP card. Meanwhile, it only drew 4.9 million viewers under age 50. (The average episode of Jersey Shore attracted 6.2 million under-50s last season.) Plus: Kevin Costner and Tom Berenger are big '80s stars, and their fans tuned in, says James Von Schilling at The Christian Science Monitor.

2. Strong brand building
Niche cable channels, including Bravo, AMC, and History, have brilliantly leveraged one hit series into a promotional launching pad for an entire line-up of similar programming, Syracuse University professor Robert Thompson tells the C-S Monitor. Bravo turned the breakout success of Queer Eye for the Straight Guy into a uniquely branded channel; AMC did the same with Mad Men and its slate of prestige dramas. History heavily cross-promoted Hatfields & McCoys during its surprisingly high-rated reality show Pawn Stars, and scored. 

3. It was event TV
Hatfields & McCoys was classic entertainment, and sometimes that's all viewers desire, says Gloria Goodale at the C-S Monitor: "The high production values, the big-name stars, and big budgets." The series had the "old-fashioned appeal of a classic network miniseries," says Greg Evans at Bloomberg. "No Deadwood here." And DVRs make the idea watching an epic, six-hour miniseries all the more appealing, says Contact Music. Viewers can watch the three episodes on a delay in marathon sessions.

4. The feud fascinates people
Interest in the bad blood between the Hatfield and McCoy families clearly hasn't waned over the years, says Bill Carter at The New York Times. The large following for History's miniseries also sparked a surge in sales of books about the clashing clans. The day after the final installment of the miniseries aired, four Hatfield and McCoy books were among the top 10 "Movers & Shakers" on Amazon.