Those were requested be removed by the DCCC themselves, not Twitter. The OP's point stands.
Sounds like the DCCC pointed out to Twitter that these accounts were violating Twitter’s terms of service and Twitter agreed. Twitter made the decision to remove the accounts.
What terms of service would they be violating? There are automated bots all over Twitter. Telling people to not vote is not hateful, it's not obscene, there's nothing wrong with it. It's full on censorship of ideas.