It may seem like common knowledge to us, but it really isn't in some places of the world. For instance, in Japan, this symbol means something completely different — a Buddhist symbol.
People prioritize what's most relevant to them and what has affected them the most. This is why Koreans spend more time learning about Japan's Rising Sun symbol and how Japan has historically hurt them instead of what Nazi imagery looks like.
There's really no reason for them intentionally cause public outcry by doing something like this, if that's what people are speculating. There's no incentive for them. This appears to be an instance of lack of awareness and that's what it is.
I should link my three knowledge threads huh? lol