I agree with some of this. For sure, he should've done a lot more to to keep the deranged cult in check.
Way more. That's my main issue with him. Things looked promising here at first, when he denounced the Berniebros and said he didn't want support from misogynist bullies. But this eventually fell by the wayside as the primary began to heat up and there was no benefit to attempting to stave off the crazy, as it would just dampen "enthusiasm" (ugh) and cause negative headlines. It was a political calculation for sure. This toxic negative atmosphere then began to fester even more, when suddenly every Hillary win (seriously, like nearly every one) was denounced by the cult as election fraud. They really jumped the shark when they accused Hillary of "suppressing the vote in Arizona" when the Republican government is the one that cut polling stations. Still nothing from Bernie. He talked about the "system being rigged" in terms of superdelegates, wealthy contributors, etc. but his supporters took it as proof that Hillary was rigging the vote and was a reptilian or whatever, and he never fought against these conspiracies, at least not sufficiently. His response to the NV convention was inexcusable. "Bernie or Bust?" Still nothing. I also agree he should've dropped out once it became obvious he couldn't win, as it only fed the delusion and Frankenstein monster of the cult even more. I get that he wanted to influence the platform and direction of the party, but you can easily make it clear that is your goal, rather than feeding the delusion by pretending you're still going to win.
However, I think you're overestimating the extent to which he had iron fist control over his deranged cult. I mean, this is the same group that is now calling him sellout traitorous corporatist filth and sending him death threats. I kind of doubt that was part of his "master plan." As for Bernie taking advantage of the media's Hillary hatred, well, that's politics for you. Obama admitted to doing the same thing. Hillary is not exactly an angel politically either. I don't really hold that against him. As "negative" as the primary supposedly was, neither of them ran a single negative ad, which actually makes it historically positive in the grand scheme of things. It was mostly social media creating a toxic atmosphere, which wasn't present as much in 2008. But I bet, sadly, that it is the new normal. I highly doubt it will be exclusive to Bernie. In addition to that, I think the deranged cult springing up was inevitable to some extent. He could've done a lot more to stem the crazy as I said above, but I don't think he had the ability to stop it altogether. And I'm highly skeptical the entire thing was an astroturf campaign by the Sanders campaign as you seem to claim, for obvious reasons.
So although I'd say overall his campaign was in HP territory, I did have a lot of respect for him beforehand for fighting for progressive goals in Congress for decades. As an independent (and presumably a centrist) I can see why you wouldn't necessarily feel that way, but it's why a lot of progressive Hillary supporters still have respect for him even after this primary.