In the rust belt. Full stop. Young people, blacks and Latinos stayed home. If you doubt me 538 had a meticulously sourced article on the subject. Hilary was arrogant. She assumed no sane country would elect Trump. She was wrong, and we're all gonna pay for it. For God's sake people, vote in your mid terms.
Nate Silver is a smart guy, but he relies too much on the models and not the context or the assumptions.
The actual context is that Hillary lost the popular vote by a small margin, which means that *any* of about two dozen reasons could have flipped the election the other way.
It's like viewing a stack of books one inch higher than another stack, and saying that the reason is a specific book halfway up isn't big enough.
The reality is that Clinton could have done better in any one of : her political dealings during the election (getting debate answers, screwing Bernie supporters, superdelegates, and so on), her financing and backing (Moroccan meeting, Saudi donations, Soros), her image (not attending rallies and letting others do her campaigning for her, coming across as cold and unfeeling, "I feel your pain"), or her past actions (the server, her actions during Benghazi, Russian unfreeze, Clinton Foundation shenanigans).
It's hard to imagine Trump doing better in any of his several categories (meaning: there's nothing he could have done to mitigate).
Pretty-much any one of these would have upped her popular vote by the 1% she needed to beat Trump and win several more electoral colleges. The reliable polls pointed out that she had some 1024 ways to win, while Trump had only four.
538 isn't the oracle of prediction that everyone thinks it is. Nate's basic premise is that "past performance predicts future actions", which has been completely disproven this year.
So for example, Nate predicted that Trump's presidency would go down in flames early last year, predicted 80% chance Trump would lose the general election, and noted that Congressional endorsements are the best predictor of the primary candidate; meaning, Ted Cruse would win the primary.
538 is racking up a long list of failed predictions.