Because their world ranking was 5th which puts them outside the top 4 rankings of USA, Canada, Finland, Russia. The brackets are so they don't have massive blowouts and give a chance of those countries to get wins and grow the sport in their country...which should be obvious when both teams from group A (Finland/Russia) smoked the two teams from group B (Sweden/Switzerland).
Switzerland and Japan got in by beating everyone else in a qualification tournament which is why there was no Germany this Olympics, Korea got in as a host nation and were obviously going to be trashed by everyone given their world ranking.