The documentary went into some of the historical background, it was actually kind of interesting. The Korean Government is aware that while Korea has a good reputation as a technology/business economy, it has virtually no global presence in a cultural sense. So for the last 10 years or so the Korean government has been pouring funding into building up the Korean pop music industry, trying to develop into a cultural export. Gangnam style is the first breakthrough that has moved beyond the normal k-pop circles and become an outright multi-country global hit. The Korean cultural ambassador and apparently other elements of the Korean government apparently views Gangnam style as an opportunity to promote Korean culture generally and appears to be mounting a full court press, globally.
They had Ban Ki Moon appearing with Psy yesterday in a big photo op, for example.
They literally appear to believe that Korean cultural exports will augment brands like Samsung and make Korean products more attractive / stylish. So Gangnam style.... appears to be part of a national strategy.