I’m not in the habit of giving stock tips or making market calls. I’ve never claimed to be an investment strategist. But after spending years reporting on business and finance, I was convinced on the night of Nov. 8, 2016, that the conventional market wisdom was way off target.

As the night wore on and equity traders began to grasp that Donald Trump would become president, stock markets around the world started selling off. In the U.S., trading in S&P 500 futures would eventually be halted after a 5% decline. After midnight,...