Two tournaments with identical entrants can produce different winners because of their structure alone. Format decides how much variance is allowed to influence the outcome.
Single elimination maximises variance
One loss removes a team, so a single poor game ends a tournament regardless of everything before it. The format samples each matchup once.
That produces upsets, which is entertaining and is a legitimate reason to choose it. It also means the winner is not reliably the strongest entrant.
Broadcasters favour it because every match carries elimination stakes and the schedule is short and predictable.
Double elimination buys a second sample
A lower bracket gives beaten teams another route, so one bad game is survivable. The format is more likely to produce the stronger team as champion.
The cost is scheduling. The bracket roughly doubles in length, and lower bracket teams play many more games than upper bracket ones.
That asymmetry is itself a factor. A team arriving at the final from the lower bracket is more fatigued and often faces a game deficit by rule.
Series length compounds skill differences
A single game between close teams is close to a coin flip. Extending to a longer series requires the weaker side to repeat an upset.
Longer series also reward preparation depth, since teams must show more strategies and adapt between games. A one-trick roster is exposed.
This is why finals are longer than early rounds. The format is tuned to reduce variance where the result matters most.
Group stages test consistency instead
Round-robin play gives every team the same set of opponents, which separates consistent performance from a single strong day.
The weakness is that late matches can be meaningless, and a qualified team may rest players or hide strategies. The information the format produces degrades at the end.
Tie-breaking rules then decide qualification on aggregate margins, which encourages teams to play differently from how they would in a bracket.
Seeding determines who meets when
Placing the strongest teams in opposite halves of a bracket keeps them apart until late. Poor seeding can eliminate a leading contender in the first round.
Because seeding is derived from earlier results or regional allocation, its accuracy varies. Regional slots in particular can place uneven teams at the same seed.
Understanding the format therefore explains more about a tournament's outcome than most post-match analysis does. The structure was set before anyone played.