I think the ratings could be a little misleading. The tournament is seeded to that in R1 there is a larger skill difference between players (in theory), and this skill difference reduces at the tournament progresses.
This could mean that a civ such as the ethiopians were consistently picked by the weaker player in the match and consequently lost more often.
This could mean that a civ such as the ethiopians were consistently picked by the weaker player in the match and consequently lost more often.