Not to mention their servers were located in a US datacenter, which means they can quite easily demand to seize the hardware. Not the brightest idea to host it there to be honest.
Which US datacenter where the servers located in?
They were hosted by Cloudflare which is a US company. Exactly where the servers where physically located I'm not sure, I think I read somewhere in the US. But either way, as Cloudflare is a US based company the FBI can demand pretty much anything from them under US law and they have to comply, even if the servers were physically located abroad (which I don't think they were, I think it was a data center in california).
Cloudflare doesn't host websites, it's a distributed caching proxy service for speed and DDoS protection, plus DNS services.