Analyzing the surprising election results, Daily Kos says
There were no “hidden Trump voters” who crawled out of a cave on Election Day. There were simply Democratic voters who didn’t show. In Wisconsin alone, a quarter of a million voters … didn’t.
The result was a razor thin margin in enough states to change the outcome.
And there was another problem with the Democrats' strategy:
Wisconsin received exactly zero visits during the general election. Previous to Comey’s letter, the Clinton crew was so focused on expanding the map, they failed to nail down the basics.
On the effect of FBI Director Comey
Only 13 percent of the electorate made up their minds in the last few days, but those were these days ...