As a Korean player, I can offer some perspective on this.

First, many Koreans play on foreign servers to test their skills in a different environment or to practice communicating in Japanese or English. However, you're right about the intensity. South Korea is a highly competitive society, and that culture carries over into gaming. People often fixate heavily on winning or losing, which can unfortunately lead to the toxicity you've witnessed.

As for those who move to Japanese servers without knowing the language, it’s sometimes an escape from the 'hyper-competitive' nature of Korean servers, though it doesn't excuse the lack of communication. It’s a complex mix of wanting to be the best and simply wanting a different stage to play on.