They also didn’t understand that, as nice as it would have been, the 1990s couldn’t last forever. A lot of them still don’t understand that and are operating as if history ended sometime in the mid '90s.
Also, the establishment constantly counts on having incredibly charismatic and smooth candidates like Bill Clinton or Obama, when the norm is more someone like Gore or Kerry or Hillary Clinton or Biden.
Alinskyism posits that 30% is only the first step, a strategic compromise with the opposition on policy to help win elections. That’s as far as the DLC was ever able (or I’d argue, willing) to go because they’d committed to the neoliberal consensus and were operating out of pants-pissing fear of not being conservative enough on economic, military, and law-and-order issues and out of briefs-soiling terror of offending big-money corporate donors. And thus you had the chair of the supposed duopoly party of the left also being a political shill for the payday loan and private prison industries.
What “darkness”? There are several proven models to choose from for single-payer universal and free or subsidised college tuition that have been in place for decades in other OECD countries. The same goes for financial and corporate governance regulation. And the Green New Deal is modeled on the original FDR-era emergency programme (with a bit of the post-war space programme mixed in). The details have to be worked out and there’s room for some compromise between the establishment and progressive wings of the party, but this isn’t a leap into complete unknowns.
If there’s darkness, it’s smoke being generated by the GOP and the corporate media. With the not-unrelated threats of health care costs that regularly bankrupt families, growing inequality, the resurgence of right-wing populism, and global warming threatening the country we need a rush of fresh progressive air to blow away the conservative/Libertarian miasma of FUD that claims progressive policies aren’t possible in the U.S. because “reasons”.