Three political scientists (Sides, Tesler, and Vavreck) studied the question of whether Clinton ran a competent campaign, and concluded that she did; none of her campaign decisions contributed significantly to her loss. I think that’s better than a few anecdotes, or your personal impression, don’t you? I’ve heard a few bad anecdotes myself, but most of the bad anecdotes are in support of second-guessing by people with hindsight, and who weren’t looking at the polling the campaigns had. It’s hard for a campaign to plan for something like the Comey letter. Hillary had to campaign on the information she had.

The idea that Bernie would have won is a comforting story that Bernie supporters tell themselves, but there’s no good reason to believe it. Bernie only ever ran one national campaign, and he lost — badly. He lost because he had insufficient support, or because he didn’t adequately turn that support out, or a mix of both. If he couldn’t beat Hillary Clinton, what makes anyone think he could beat the person who beat Hillary? He was never properly vetted by the press or political opponents; Hillary held back on attacks because she expected to win without them, and didn’t want to alienate his supporters. The GOP would not have held back, though. For example, we have no idea how much Bernie’s self-applied ‘socialist’ label would have hurt, but it would have hurt. Your claim that Bernie was notably good at turnout is dubious, not just because he lost, but because he lost more when participation was higher. 2016 saw two states (Washington and Nebraska) that held high-turnout primaries and low-turnout caucuses; in both cases, Hillary won the primary and Bernie the caucuses. He depended on caucuses for the majority of his state wins. So in fact he appeared stronger because of voter suppression; that’s not the way a masterly GOTV campaign looks.