In the 2012 election, the polls that had made Mitt Romney so confident that he was going to win were his own internal polls, based on models that failed to accurately estimate voter turnout. But the public polls, especially statewide polls, painted a fairly accurate picture of how the electoral college might go.
Donald Trump, having spent decades in the public eye as an entertainer, may not understand what the nuclear triad is, or what America's 'first use' nuclear policy is, or why starting a trade war would be a disaster. But he does understand storytelling, the power of a clear narrative, and the importance of stirring emotion.