"In 1861, Jay Cooke, a minor money man hoping to help the Union army, lobbied Abraham Lincoln’s government to make investing accessible to more Americans. In 1972, Bill Gross, destined to earn the nickname “the Bond King,” realized that more value could be squeezed out of the products that Cooke wanted to sell — government bonds — if they were traded by experts. And in 2021, a Reddit user named Roaring Kitty led a band of regular Joes on a crusade against financial engineers of Mr. Gross’s ilk."