If the only way for the Democrats to win is to become populists, and the point of voting for the Democrats is to defeat populism, then what can voters do other than bow down to their new populist overlords?
The people want a lot of stupid shit. They want cheap food, but also to deport the people who harvest it cheaply. They want a balanced budget, tax cuts, and no reductions in spending. They want to eliminate drug abuse, by doubling down on the policies that have made drug smugglers and producers unimaginably wealthy and powerful.
It's impossible to give the people what they want; Not merely politically difficult, but logically and mathematically impossible.
Trump got elected by promising it to them anyway. Harris got defeated because she wouldn't promise anything that was very obviously and indisputably impossible, just because it was popular.
Reality based policies cannot win, if the electorate no longer believes in the objective existence of any reality. And policies that fly in the face of reality are disastrous, regardless of what party tries to implement them.
Abandoning reality, even if that is the only path to victory, is not an option for any sane elements of any polity.
Trump won because enough voters are insane, and enough sane Americans didn't vote against him - presumably because they didn't know, or didn't believe, that Trump would actually try to implement his insane platform.
Most of the supporters of the Leopards Eating People's Faces Party are still expecting that their own faces will be exempt. They are slow learners, and will be shocked and angry when they discover the hard way that there were never any exemptions for non-billionaires.