This election analysis I think is pretty accurate to explain how the masser voter turnout during the recent South Korean Presidential election led to a decisive Park Geun-hye win:
Park Geun-hye won the presidential election on Wednesday partly thanks to the massive turnout of older voters, pundits say. Turnout of voters in their 50s was 89.9 percent and of those over 60 it was 78.8 percent, far higher than among voters in their 20s through 40s.
Exit polls showed that 62.5 percent of 50-somethings voted for Park, making them the determining factor in the election.
Pundits point to a widespread sense of anxiety among older voters. They tend to worry more about current affairs than other age groups, said Prof. Lim Seong-ho of Kyunghee University. “They voted for the candidate who made them feel safer about the economy and North Korea,” he added.
Pundits also speculate older voters were uncomfortable about the influence of so many old confidants of former president Roh Moo-hyun in Democratic United Party candidate Moon Jae-in’s camp. Some say they feel anxious about national security, including well-timed claims from the Saenuri Party that Roh was willing to give up the Northern Limit Line, the de facto maritime border with North Korea.
“The North Korean issue, and especially Roh’s alleged remarks, was one of the deciding factors, whether the story is true or not,” said Prof. Yoon Pyung-joong of Hanshin University. “Older voters have more vivid memories of North Korean provocations than those in their 20s and 30, who didn’t experience the Korean War, so they are keen on national security.”. [Chosun Ilbo]
You can read the rest at the link, but another factor from the analysis is that older voters remember the Park Chung-hee days favorably. I always find it interesting how the people that were old enough to experience the Park Chung-hee years always seem to have a more favorable opinion of the dictator than those that were too young to experience his rule.