It's part of the current DNA of the Democratic Party:
From 2019:
The celebration of charismatic, conflict-averse uniters in Democratic-led White Houses (Clinton and Obama) omits a key, and punishing, shift in Democratic politics from anything resembling a viable effort to build a long-term majoritarian liberal coalition. Over the past two decades, Democrats steadily lost disaffected former supporters, while failing to consistently mobilize young or economically precarious people alienated from the entire political process, as the Republican Party increasingly became a nihilistic, anti-democratic machine designed to bamboozle a white elderly base and thwart the desires of the larger public for the sake of an entrenched oligarchy.
All the while, Democratic leaders continue to campaign and govern from a crouched, defensive position even after they win power. They have bought into the central ideological proposition, peddled by apparatchiks and consultants aligned with the conservative movement, that America is an incorrigibly “center-right” nation, and they have precious little strategy or inclination to move that consensus leftward—to fight, in other words, to change the national consensus; the sort of activity that was once understood as “politics.”
https://newrepublic.com/article/154113/democratic-party-fighting-spirit-give-war-chance