It wasn't because of natural resources or oil.
It wasn't any modern industry that just had to recover after the war such as Germany or Japan did. South Korea had NO modern industry of any kind, higher education institution, a modern workforce, effective government agencies, etc. S. Korea was literally a hell hole of a nation in 1953.
After the WTF period Koreans went through from 1910 to 1953 (after having had a 500 years long kingdom, the Chosun dynasty), South Korea just had to do what was necessary to survive.
And only way they saw how was producing a workforce to be productive. And no, Montessori method was not a viable option.
You don't have to be a highly educated non-Korean to see the education system is not quite right or wrong. Many highly educated and even not so highly educated people IN S. Korea know the question is valid to ask. Some want a change. Many who immigrated out of S. Korea to US and other nations list 2 reasons for leaving the nation, 1) conscription army and 2) the college entrance exam, the Suneung. But it was a system created at a time when there was no time to debate, but to act quickly to produce a workforce, just to survive as a nation. And it has delivered so far.
Yes the suicides are tragic. But consider this. Far more S. Koreans have died (including newborn, young, old) from lack of basic medical care in South Korea when only select few had access to modern medical care up until 1970's, 80's. The nation and citizens couldn't pay for it, for lack of wealth, from due to lack of skills needed by a modern workforce. But now that they can afford it, a nation wide medical care system is in place. Without educating the workforce (and yes the Suneung), they wouldn't have that luxury.
Easy for you to say they should be ashamed of that. I quite disagree.