I believe former President Chun (Shouldn't it be Jeon?) Doo Hwan "gave in" to U.S. demands (by President Ronald Reagan) that S. Korea should hold free and fair elections before holding the Olympics in 1988. This makes sense on a number of levels as you should think about what was going on in 1980-81. The United States naturally wanted to make sure that South Korea at this time was:
1. Prosperous (in 1980(or 81?), Japan under U.S. pressure, gave $4 billion in unconditional aid to South Korea to avert national bankruptcy.2. Free (Democratic).
With free elections being held in 1987 and Koreans at this time actually choosing to elect another member from the military establishment (and along with the inability of the three Kims to agree on a unified candidate and the dynamics of regional politics in Korea) the U.S. should get much more credit for the establishment of democracy in Korea. I say this as demonstrations by the Korean middle class that led to Kim Young Sam's election was actually the 2nd free and fair election. Nonetheless, it may be hard for South Koreans to accept this, but even as the U.S. military didn’t intervene and only watched as South Korea’s populace was at times brutally repressed (Gwangju), the U.S. had a natural interest to ensure that South Korea was both free and prosperous.
That’s why even as the U.S. military didn’t intervene, former U.S. President Ronald Reagan pressed for democratic elections and pressed Japan to give aid to South Korea unconditionally). As you may very well know, the Olympics in 1988 were a success with boycotts coming only from North Korea and Cuba. Remember, in 1984 (Los Angeles, nations in the Communist bloc boycotted in retaliation for the western world boycotting in 1980 to protest Soviet Union’s invasion of Afghanistan). By the way, a little bit of hometown pride here, it was the second time Los Angeles hosted the Olympics. Imagine that. With all the cities in the world, L.A. was chosen twice. So, I think it’s fair to blame the U.S. (a little) for just watching the brutal repression going on at the time, but at the same time you should also be able to credit the United States for South Korea holding free and fair elections. If that makes sense…
Also, I forgot where I read this, but if you take a look at any tourist brochure, and look at a map of Seoul you don’t see any reference to a base that is at the heart of the city. So, I can definitely feel this. I can’t imagine if there were foreign soldiers in Washington, D.C. or even Berkeley for that matter (though I hear the city passed an ordinance/law that makes it illegal for the U.S. army to open up a recruitment office in the city?)