Left-wing instances were defederated preemptively, as a last resort because the admins feared they would “dismantle western propaganda”. Right-wing instances were defederated after they wouldn't moderate their users posting CSAM, gore, and nazi shit.
They aren't always defederated. Most users can still use [email protected], but most don't bother because absolutely nothing ever gets through to the conservative users of that community no matter what sources or evidence to support arguments are used. It's like talking to a brick wall. Some of the users like MomoTimetoDie are outright hostile.