Well, since nothing any of these groups are doing is even illegal, operational security is nice, but really not necessary. But even if you have the technical aspects conquered, there’s no effective way to vet people for being True Believers that wouldn’t simultaneously doom your organization to low membership and paranoid infighting.
And if anyone is doing things that are illegal, organizational silos were a thing even before the internet was a glimmer in Al Gore’s eye, see: terror cells. The Battle of Algiers is a great movie that goes into how it works.