Basically, Korean baseball, like other Asian baseball (Most notably Japanese) has a lot of charging the mound. It's allowed, you don't even get into that much trouble for it. If the pitcher stands his ground or backs off, or gets angry or serious the batter considers him to be admitting to hitting/crowding him on purpose and a brawl starts but it's the pitchers fault. If the pitcher does something goofy or apologizes the batter can still choose to fight but it'll be his fault. Which is why you see some crazy mound charges like when a guy charges the pitcher and the pitcher backs off hands up apologizing and then the batter just runs around in a huge arch past the mound and first base into his dugout while pointing at the pitcher and laughing. It's all about who is gonna admit they were wrong. The pitcher in this acted goofy to admit he had fucked up. Batter and them did a crazy dance then the batter took his base. If that hadn't happened there would have probably been a fist fight.
Note; It could have also been a joke from the very beginning, but still Asian baseball has some crazy stuff in it like that.