I wonder about this. If a government can hack into a server and steal the private encryption key, then they could just look like any other server in the server farm, right?

Given the recent Shadow Brokers release of the NSA tools, it seems to me that this was not only possible, but probable (not necessarily with Wikipedia, but any website).

Well, they can block it whole. Once they figure out they can't block parts that's exactly what they will do. Either that or a re-host on their own infrastructure with the offending parts removed, conveniently seizing whatever domain names wikipedia has in that country for added authenticity.