There are two candidates I can think of that may fit.
"To the victor go/belong the spoils".
The winner is entitled to all of the rewards, bonuses, or benefits of
success. (A variation of "to the victor go the spoils.")
Farlex Dictionary of Idioms
The winner gets everything
American Heritage Idioms
It's funny that this phrase also has a connection to voting and politics, particularly the:
The postelection practice of rewarding loyal
supporters of the winning candidates and party with appointive public
American Heritage Dictionary
So there we go, we simply can't escape election terminology, it seems.
Another has many variations, but can be said:
No one remembers who came in second.
Interestingly it was tweeted by Donald Trump in 2016, and reported by the Daily Mail as "No one remembers second place." Sometimes said "the guy" or "the second guy".
This phrase reminds me of many things, but possibly most of all Edwin E Aldrin, as he is probably the best counterexample of this supposed aphorism.
The idea of no one remembering who came second (I conjecture) must have been in people's conscience for a long time, as between 1969 and now, "someone" (maybe a higher power) has continued broaching the topic of Buzz Aldrin being the second man to step on the moon. As a result, as far as I know, he's a household name, which name has been immortalised in this guy:
Just kidding, his name was immortalised before Pixar/Walt Disney created Toy Story.
Sometimes it's not even the second person who is unknown in popular culture, but also co-discoverers who made a discovery at the same time.
List of multiple discoeries