Because these countries have relatively few vulnerable coastal cities, and a lot of land that's too cold to do much with. Yeah some places will get drier, but some will get wetter too (I think overall it gets wetter, but that doesn't mean much to people in areas that turn into deserts.)
Anyway I like to talk to people about it because I've noticed a very visceral reaction among progressives (translation: it gets down-voted on HN) that there could be any "winners" in climate change. It has to be all bad. They might well be right, but I think my point is still valid. Again, I'm not sure these countries will "win" but they'll be relative winners in a game full of negative prizes. If you disagree, engage with me, don't just click on the arrow.