Hillary Clinton's nomination is usually explained in terms of her advantages in super-delegates and in fundraising. But she had those advantages in 2008, and still lost.
The difference in 2016 is that she had identity politics on her side. She ran a campaign based on hating white people, and she picked of the votes of the blacks, hispanics, and other non-white groups. The polls showed that Sanders won in white states, and Clinton only did well in areas with a lot of non-whites.
This is also my impression from listening to a lot of Clinton and Sanders supporters. I never hear any Clinton supporters say that they like her personally, or that they prefer her policy positions, or that they find her trustworthy, honest, or competent. I have never even heard anyone agree with her foreign policy.
It all comes down to identity politics. They want her because she is pro-feminist and aligned with anti-whites. She is the most racially divisive candidate since the segregationist Democrats of the 1960s.
So vote for Hillary Clinton if you want a race war.