The U.S. presidential election: Big data prognosticators failed badly

In the last few election cycles, code-driven tools were fine-tuned and their projections were, indeed, remarkably accurate in important elections worldwide. Machines calculated the probabilities, and no pundits with experience and inside contacts were asked to tell us what was going to happen.

The process was clear: first gather historic and current data, write the code you need, and run regressions. What happened this year when predictions failed so badly?