Hillary's mistake was trying to denounce Bernie as as crackpot and alienating his base, which as shown by the election was a huge part of the Democrat's constituency. I don't think Bernie was 100% correct about everything, but he clearly represented the overall values of the Democratic constituency, and rather than appeal to Sanders' base, Hillary made the ridiculous choice to ignore his supporters and try to win over conservatives with people like Tim Kaine, and use the threat of Trump to coerce Democratic votes.
Which of course leads to her main fault. Trump's candidacy was the ultimately result of her failed "pied piper candidate" ploy to essentially coerce the country to vote for her. The result of the election was essentially Hillary's own failed extortion gambit. It was this revelation, that she would be willing to unleash a monster like Trump, that made me not vote for her.
I despise Trump and his terrifying ignorance and greed, but I view Hillary as just as bad, although definitely not worse, than Trump. Considering how he and Hillary seem to have a similar love for Goldman Sachs and the Saudis, despite both claiming to be against corruption and terrorism, I'd say Trump and Hillary are equally deplorable.