They probably haven't tried stealing customer funds nor market manipulation, it's just that I think they are taking the matter personally. They might have been alarmed to large volumes of crypto trading and many profits made by crypto users from it. the statement that made me think that they are really acting based on the subjective opinion of their government official is this:
The barrage is alarming official including Prime Minister Lee Nak-yon. He says that cryptocurrency might corrupt the nations youngsters.
I think that's just normal behavior for a leader.
If you will subject your businesses (including the citizens) for a regulation I'd think it's only appropriate starting with the bigger and most known.
Also, it will be a good example for the lower level types to pursue & follow these rules.