Too many cooks spoil the broth, but many hands make light work. Can someone please explain to me why this broth, made by far too many cooks, was both labour-intensive and delicious?

"Brevity is the soul of wit" is an idiom, not some sort of undisputed fact. Your question doesn't highlight an interesting contradiction; at best it will be interpreted as a weak play on words, and at worst it will be interpreted as trolling.