To illustrate what I'm thinking of: suppose Alice and Bob are the two best players in the world at [sport]. They regularly meet in tournament finals where their matches are like a coin flip - each wins about 50% of the time. However, in major championship finals, Alice somehow always beats Bob. She's been crowned the World Champion five consecutive years in a row, beating Bob each time.
The sixth time around, Alice decides that Bob (with whom she is good friends) deserves the title as much as she does, so she concedes the final, effectively making Bob champion.
I'm wondering if this has ever happened before in any sport. Presumably, Bob never winning the championship would be a pity; on the other hand winning the championship by concession sounds like a very disappointing way to win.
The closest I know is in Magic: the Gathering, which is a card game. The tournaments use the Swiss matchmaking system, and at the end of all the rounds, there is a "cut to the top 8" where the top 8 players contest knockout matches. Conceding prior to the top 8 to a friend who still has a chance to reach top 8 is quite common (example):
With two rounds remaining, I knew I was locked for Top 8 and so my focus shifted to trying to secure the top seed so that I could choose to play first in game one of each of the Top 8 rounds. After doing some math, I realized I would be a lock for at least the second seed even with a loss and a draw. I also noticed that among the nine players with three losses, almost all of them were friends of mine. So at that point I made the decision to concede to whomever I was paired against in round 15. The pairings would then basically act as a random generator to decide who gets a free win into the Top 8. Andrejs Prost ended up winning said lottery and I followed through with my decision and scooped him into a position where he could draw into Top 8 in the final round.
I'm not aware of any concessions in the top 8 itself, though.