1. Why would an American / Canadian prop firm want to trade Korean equities?
=> Time difference. Korean market opens at 8 pm EST and closes at 2 am EST. (with current daylight saving) There are some firms out there that would want to run night trading desk to extend the hours of trading and to maximize profit-generation, as long as there is an accessible market with affluent liquidity.
2. I know Samsung, LG, and Hyundai Motor. But ain't these pretty much it about Korea?
=> Rethink everything. Korea is the no.6 economy in the world with the biggest market cap within the MSCI-emerging market countries. Debate is hot on the street on whether we should categorize Korea as emerging or as developed economy.