(Assuming these people aren't idiots). You don't know if they have any kind of reverse proxy setup beyond that. Even if they seize whatever server has the IP that Cloudflare is proxying they might just find an nginx server that's only a reverse proxy. If they alternate servers periodically and locate them in non-cooperative jurisdictions then they can prevent the government from finding anything useful. If they get kicked off Cloudflare they'll just go to DDOS-Guard. WHOIS data will probably lead them to njal.la, a person that does not exist, or some other domain nominee service. Nice right?