Last Friday a crane collapsed in lower Manhattan, killing a man named David Wichs. The next day the papers told the story of his life: a Jewish immigrant from Czechoslovakia; a math whiz with a degree from Harvard; a thoughtful neighbor and husband; “the nicest, most trustworthy person that I have known,” according to his boss, Mark Gorton, of Tower Research Capital. Mr. Wichs was just 38 when he died.

I never met Mr. Wichs, but reading about him reminded me of so many people I know in his industry—prodigiously bright and slyly...