The betting markets were not good predictors, but they weren’t trying to be. The online bookmakers that fielded bets on the election saw their largest single-event windfall ever. To understand why, you need to understand election betting and Donald Trump supporters…

The odds-shifting bonanza on election night, with all that money on the line, was not a sign that the oddsmakers knew something the mainstream media did not. Instead, the Trump spike was the peak of a phenomenon that had been unfolding all year. Many Trump supporters were certain he could not lose, and they plowed so much money into betting on him that they distorted markets in his (and ultimately, the sportsbooks’) favor.

“It’s the most irrational market I ever saw,” says Collin Sherwin, a Tampa, Florida–based gambling writer who covers the industry for Vox Media’s DraftKings Nation.