I agree that Sanders routinely overstates the broadness of his appeal, but please do find me a politician that doesn't.
Further agree that Clinton hatred played a very large role in 2016, and in making Bernie known and popular.
That said, the rest of Galts article is a mixture of shameless revisionism and outright nonsense.
For instance, if you look at the polls, more Democrats like Sanders policy than Biden policy. Literally the only reason they are voting Biden is because they think he is more electable, despite actually preferring Sanders "radicalism," known everywhere else in the world as standard center-left politics.
Note how quickly people forget how unprecedented of a swing this was - never before has a nominees fortunes changed so fast, for so little fault of their own.
It is almost as if stuff like global pandemics being managed by an illiterate orange-stained retard makes voters more conservative in their choices, with an increased preference for stability and known trajectories. And since an absolute majority of Democrats like Sanders policy over Bidens, I'd wager that policy preferences did not drive the votes away from Sanders did. Plain old fear did.
Fear of Trump winning, stoked relentless by centrist Dems, who are well-known experts in defeating Trump. Fear of coronavirus. Add in some well-timed open interference by party centrists to seize momentum on Super Tuesday, an effective strategy because primaries are football matches or some sort of twisted political Survivor show for Americans, and you've got a much more rational explanation than this hot take.