I don't read it regularly, but The Economist is a great source that covers pretty much every corner of the world. In fact I don't subscribe because its just a firehose, and I just can't keep up with the internal squabbling of parties all over the world.

I went to check to see if its available online- even via my local library, but it seems The Economist was pulled from major online sites around 2023 due to their pricing model. So I can't verify if this was covered. That said, what information has trickled out points to this being a big surprise, so there may not have been storm clouds brewing that could have foretold this.

Edit: Got past the paywall on the site and did a search and there appears to be no articles published that would have predicted an issue like this: https://www.economist.com/search?q=south+korea&sort=date&pag...