I prefer the wikipedia take on the same expression, both on the economics/efficiency standpoint as well as the banana example, but I agree that my interpretation might be too liberal for some.
https://en.wikipedia.org/wiki/Race_to_the_bottomI would summarize by stating that the
mining competition naturally drives the overall profit opportunity downwards.
This happens both quantitatively (with more miners competing, there's less profits for each/all of them) as well as qualitatively (each new miner improvement - hardware or software - further denies profits to all the existing miners that do not enjoy the same improvement).