Hillary didn't lose because Sanders people didn't vote for her- she got 80% of the votes of Sanders voters who did vote, which was a higher percentage of Sanders voters than Obama got of Hillary voters in '08.
Hillary lost- and we all know the race was lost in the firewall states because
1) She gave in to Obama's demand that the platform not pledge to stop the Trans-Pacific Partnership- an economic royalist trade agreement that the American labor movement opposed as a virtual block because they saw it as endangering jobs- and being at least willing to support ratification of TPP gave Trump his biggest wedge issue among normally Democratic working-class voters;
2) A sizable number of 2008 and 2012 Obama voters switched to Trump, mainly because Hillary came across as dismissive of working class concerns on economic issues;
3) Black turnout plummeted from 2012 and 2016, and Bernie, who was not supported by most Black voters, largely due to the false accusation that he didn't care about racism, bears no responsibility for that at all.
It's time the false accusation that Sanders supporters threw the 2016 electoral college results to Trump be put to rest, once and for all. It was large sectors of the traditional Democratic base who didn't support her, and the Democratic Party isn't going to fully recover from that until it admits that Hillary's own stand-for-nothing, just-demand that-people-vote-for-her-because-she-was-somehow "owed" the presidency was the major factor in the result.
Not Comey-though he played a role;
Not "The Russians"- they aren't THAT good at interfering in U.S. elections;
Not "Voter Suppression".
The cause was a campaign that could have fired up the Democratic base by reminding them of the Sanders economic justice items in the platform and pledging to fight for them- contrary to popular myth, Black voters were never against economic justice measures, they just wanted to make sure the election wasn't ONLY about economic justice, which was an entirely valid thing for them to demand- but cared only about what turned out to be a statistically insigificant voter bloc "moderate Republican women in the suburbs".
Hillary won their votes, it's true- but the result in 2016 proves there were never enough of them to justify her campaign's strategy of treating the base and the new progressive voters with Occupy values who were mobilized by the Sanders campaign- a group which was as diverse as those of any other candidate, especially among voters under 30- as though they didn't matter and weren't owed anything.
Hillary's loss is on Hillary's campaign- continuing to use it to bash the Left when the Left was blameless in it simply does damage- as does the refusal of establishment Dems to stop claiming that Sanders campaigners didn't care about opposing racism/sexism/xenophobia/LGBTQ rights and defending reproductive choice, when everyone knows there were no differences between the positions of the Sanders and Clinton campaigns on any of those issues, and also knows that many Sanders campaigners were also antiracist activists who support criminal justice reform and made BLM's struggle their own.
Hillary needs to own this- the party establishment needs to own this- and the understanding that's needed from here on in is that the ONLY enemy is the Right.