The column has many holes in it, but doesn't really offer any investigation into what happened. It is a screed on how stupid voters are, not to think like the writer.  

A couple of thoughts; the country would never have been formed, the constitution never ratified by small states had there been no electoral college, or no senate, to protect there minority voice.  The assertion that it was about slavery confuses this with the nefarious 3/5s compromise, (to delegitimize it.?) Ironic, since the writer then blasts the Hastert rule, for running over the same minority rights.
(I guess it's only a good rule if you are in the minority it happens to protect)
 Clinton's policies; having policies is not a virtue if people disagree, and about half the country does, on the benefit of these policies.
Trump, is course, probably worse, but lacking specific policies puts him in with another change cand. From 2008. Hope and change was not specific either.
People voted against a deaf political elite