much like the Brexit vote over here
No one really believed it would happen,so when they got to the booth they thought, fuck it and voted for Trump as a protest
More likely they didnt go to the polls at all. The big weakness in the polls is that far more people tell the pollsters that they are going to vote than actually vote. The pollsters dont seem to be capable of adjusting their results adequately to reflect that the stay at homes will affect one side more than the other. When its a close race the polls encourage complacency on the part of the side that appears to be in the lead.