I think it's more complicated than that; the one thing people don't bring up as much as I'd expect was that it was clear by the DNC he'd lost some level of his sway over some of his more fervent supporters.
He'd asked his delegates to not boo or be disruptive on the convention floor, and it did basically nothing because at that point they believed he was cowed by The Man and that they'd be standing up for the true principals of Bernie or whatthefuck ever by booing. They boo'd Bernie himself calling for a vote for Hillary.
The thing that's hard to articulate about the Bernie effect is that at some point it stopped being about him as anything other than a figurehead for the ideas and ideals people wanted to hardline; when the post-primary reconciliation came, it was met with resentment and a sense of betrayal and while the votes ultimately moved the way Clinton was discussed didn't.
Like, I think Bernie holding out as long as he did and pushing the way he did amped things up, but the Cult of Bernie ended up outstripping him and causing problems that exceeded the man himself. Which is a problem because for the most part the hardcore Bernie supporters realized Clinton was better than Trump (yeah that was a typo ), but the people in the weird grey in between just heard Trump is a racist and Clinton is a shill and people with pure intentions hate her, so... where's the motivation to vote?
A million things went wrong in that campaign, and two or three of them going right probably would have tipped it. But I think the problem with the Bernie phenomenon went beyond the behavior of the man himself. For all 08 was what it was, I don't remember hearing about disruptions at the DNC to match what happened in 16?