In the vain of good faith though: how is centrist democrat policy changed? A mega donor asks Kamala to support fracking and she does.
First, the Dem platform in 2024 was still the most left platform in my lifetime. Is that damnation by faint praise? ... yeah. But we also work with what we've got, and acknowledging that the Dems have become more left since the Clinton years, and even since the Obama years, is an important note to make.
Second, Harris was, unfortunately, always an opportunist ghoul. A lot of fuckery led up to her nomination, most of it the fault of Joe Biden running despite decreasing medical fitness for office (while accusations of dementia were passed around, the simple, natural slowing of the mind with age is more likely - and not really less damning, considering a president must be at the top of their fucking game considering they're the top official of an entire nation of hundreds of millions of people) and then dropping out (the correct choice, but again, only necessary because of the unwise decision to run again in the first place, while an incumbent).
Third, the way you change centrist Dem policy is by showing up to primaries, nominating progressive candidates and then getting them elected in the general. The DNC is made up of former and current party officials, not randos picked from the Country Club. They are there because they've demonstrated an ability to get elected and re-elected at some point in their careers - they are there because we, the voters, put them there. And while you can talk a lot about how moderates and conservative Dems shape the narrative, ultimately, the fault is on us, the voters, or at least the ones voting for centrist ghouls every fucking primary, for not kicking their wretched asses out.
You want Dem policy to change? So do fucking I. Elect, and convince others to elect, progressives in the primaries, and then back them to hilt in the general regardless of whether there's a sudden change of heart regarding the 'purity' of the candidate by some of your radical circles. We need to move the country left, and "It's not left enough!" may be a legitimate concern, but not when the alternative is "So let's move it right".
When Republicans are elected every fucking general election, the message overwhelmingly given to the Dems is either "Go right" or "Fuck, the country isn't ready for more progressive policy", depending on whether they're (respectively) centrist ghouls or left-leaning.
Helping this matter would be ranked-choice voting. If there are any measures in your area, please, support them - there's been limited success in this country for ranked-choice as interest in the idea has increased - including the Dem primary that saw Mamdani (MAY HIS ENEMIES BE DESTROYED) nominated. It will help many on the fence in primaries make a more progressive choice by reducing the fear of right-wing candidates eking out over moderate candidates.