It is not only in South Korea where this "crypto fatigue" can be observed. I think it is found all over the world.
There is an economic slow down all over the world and it is reflecting in the market, even for any institution or an individual to invest money they should have the funds but things are slowing down as the global economic trend is showing its weakness. I do not know whether these Korean exchanges used to represent the real trading volume and with regulations they might be forced to show the real volume and hence they came to the reality that it is not that was represented earlier, i am just speculating other than that i do not see anything.
In 2013 it was China that was the dumbest market. In 2017 it was S Korea. I wonder where it'll be next time.
The volumes were fake from those Chinese exchanges.