I think Bernie scared the establishment dems too much.

This is why I think Bernie actually had a far better chance of winning the 2016 primary than he did the totally doomed 2020 primary. (That said, I think it's very unlikely he'd have went on to become president after either primary.)

Nationally speaking, he was a no one before his 2016 campaign. He arrived so late to the primary process that until then, Hillary Clinton was the presumed victor in a similar way incumbent presidents are presumed the de facto victors in their own primaries. He did receive an unexpected amount of fanfare at his announcement, but for a while afterwards, the party essentially expected him to be a far more subdued 2020 Mike Gravel type figure who's goal is to make it into the debates, raise some domestic policy issues to help move public opinion, and drop out sometime around the first few primary contests. Probably because that was most likely Bernie's actual goal at the time.

But actually those specific issues were what every remotely left learning person struggling in this country was waiting to hear in a candidate, and his campaign exploded in popularity shortly before the voting. Hillary Clinton was the DNC's only option to contest him. They were caught off guard, and had no 2020 style shenanigans prepared to force another candidate ahead of him as a buffer. Ratfucking the Iowa caucus was their only option. If Bernie won Iowa, nothing would have stopped the momentum going forward.

That was the last Iowa caucus to have obfuscated actual vote counts. We have no idea what they were. All that we have is the Iowa Democratic party's official "state delegate equivalent" numbers. According to that, Bernie lost by a narrow margin. Months later at the convention, the DNC Bernie delegates won a vote that forced Iowa to release true vote counts in caucuses going forward.

And what happened four years later in the 2020 Iowa Democratic caucuses? Bernie won the most votes as per the previously hidden raw vote counts. But surprise, he lost the actual caucus, once again narrowly receiving less "state delegate equivalents" than his opponent, Mayo Pete this time. This fucking bullshit was immediately obvious to everyone. Within minutes of the caucus closing, everyone knew what a corrupt shit show it was when the results were severely delayed. Imagine the wild shit the Democratic party must've been doing for decades back when the caucus process was essentially a black box, theirs free to manipulate.

Normal primary elections are much harder to rig than that. It can be done, but I don't think the Democratic party had the time remaining to put in the necessary legwork. If that Iowa ratfuck failed, it was over for Hillary Clinton. I don't think they would have made use of the super delegates still having the option to choose their candidate and thereby ignore the outcome of the contests. It was just too brazen a move, they'd have been right to fear it would cause the party to implode. The Democratic establishment would have found it preferable to sabotage Bernie's national campaign as inconspicuously as possible.

They will never let it get that close again.