My point is not that they're wrong and Trump won't successfully end democracy (I think the odds are low but non-zero), my point is that the strategy blew up in the DNC's faces and should have been identified as a terrible plan from the start.

Being a Cassandra is not a winning playbook. Being able to say "I told you so" is small comfort, and that's the package they chose when they decided to make themselves look crazy to the electorate. If they believed democracy to be in danger the correct move was to nominate an electable candidate last year, not wait until Biden turned out to be unelectable and then start screaming about the end of democracy.