There are so many things that can affect the outcome of games in such a small sample. Strength of opposition, random player under/overperformance, tactical mismatches and all that stuff that you can't really predict from game to game. There's a reason there's very rarely a clear favourite going into a tournament.
Sure the side that wins it probably gets everything right over a few games but it's just odd how they're automatically good and everyone that else is bad.