Dems successfully completed their main mission; take over left-wing movements (or at least groups with potential), take them over and turn them into "voteblue" movements, then destroy them. Sure, this isn't purely the doing of the DNC (some leaders of the BLM movement were killed by cops, some sold out, some walked away), but as soon as Trump became president - especially when he started to attack Kaepernick, this started to happen. Then on 2020 election day, Dems immediately started blaming the BLM/defund movement, even after they successfully turned it into a "vote blue no matter who" movement.
The national org can beef with, undermine, confuse, and ultimately excommunicate local movements.
Its not a big deal for existing members, but this kind of co-opting undermines efforts to grow, develop, and communicate between local chapters.
Look up the history of the LaRouche Democrats. Its basically that, but for every progressive movement now.