I’m sorry but the data just doesn’t bear that out unless you you impose an interpretation on it to meet your predefined narrative. The Sanders voters who switched aren’t representative of his base or the Democratic Party as a whole. They’re people who likely would not have voted for Clinton regardless of whether Sanders was the primary challenger. You saw the same phenomenon in 2008, when about 25 percent of Clinton voters switched to McCain in the general (vs. 10 percent Bernie-Trump switchers)
An excerpt of a different analysis using the exact same survey:
The phenomenon of Sanders-Trump voters is perhaps the easiest to dismiss out of hand as costing Clinton the election. Much of the phenomenon is attributable to the function of party registration. Registration with a political party is a lagging indicator. For example, West Virginia was Trump’s second-best state in terms of vote percentage and percentage margin (after Wyoming). However, registered Democrats still outnumber registered Republicans in the Mountain State. That’s because so many West Virginians registered as Democrats when the state was still solidly blue and never changed their registration to Republican as they started voting differently. Switching party registration involves paperwork and deadlines, so less involved voters don’t necessarily get around to making a change. So in closed or semi-closed primary states like Oklahoma, Kentucky, and West Virginia, these ancestral, less-engaged Democrats can’t vote in Republican primaries. In 2008, they voted overwhelmingly for Clinton, who was running to the right of eventual-winner Barack Obama. In 2012, these states gave outsized numbers of votes to barely-funded, fringe Democrats running against Obama. And in 2016, Oklahoma and West Virginia thumbed their nose at Clinton and voted for Sanders while Kentucky backed Clinton but by less than a point.
The data bear this out. The Sanders-Trump voters didn’t self-identify much as Democrats, had approval ratings for President Obama of 23% (perhaps he’d be a better scapegoat for Clinton among this subset of voters) and were less likely to believe that white people have certain advantages in the United States. This doesn’t sound like people who were part of the Obama coalition, nor would they have backed Clinton against Trump in most instances. To be clear, there are some people in this group of voters who might have voted for Clinton if not for the Sanders campaign, but they are the vast minority, and you should be wary of anyone arguing otherwise.
