Profit is hard to define or rather it can't be looked at in isolation. Killing CoH means NCSoft can leave the North American market, 98% of their revenue is in Korea. So they can shut down their US offices, data centers, marketing, get rid of Korean personnel with N. America knowledge, Korean managers dealing with N. America and so on. Lot's of secondary costs that can be lowered or gotten rid of totally. Just saving the time and hassle (late hours, mis-communication, flight costs, etc.) of communicating with the North American offices may be worth it. So even if CoH was profitable in isolation, once you add in all those other North America costs that get saved it may very well be a loss. Either way NCSoft clearly didn't want to deal with the hassle.
Doesn't NCSoft own Guild Wars 1 & 2 (one of which is practically brand new)? Shouldn't they still need offices in North America to support them? I'm confused about how they can manage Guild Wars in North America without offices and personnel.