We're not talking about commercial off the shelf software, here, where you can just turn on the installer and let 'er rip and "next, next, next" through all the menus. At best, they can clone a recovery from their backup onto the new hardware, but then they have to spend several hours or even days manually configuring all the settings required to get a new world server (which is, in all likelihood, a cluster of servers, not just a single machine) up and running.
Then they have to add in all the support hardware for it - switches, routers, battery backups, backup systems. (Let's not forget that you have to buy two servers for every one server you use in production. Modern day backup systems are clones that can run the software just like the primary servers, albeit more slowly, with about 10-15 minutes notice.)
Then they have to test each server individually. Bring them on, one at a time. If you try to bring up all ten new servers or whatever they are adding all at once... one mis-configuration could take out the entire data center, and you won't know which server it is if you turned them on together.
Then they have to test the actual game on the server internally. Does character creation work, does the data store? That kind of basic QA testing will take another full day. Sure, a lot of that testing will be automated, but a lot of it still has to be managed by a human being, too.
So no, this is not a one day project. Once the hardware comes in (which will take 2-3 days once an order is placed since servers are usually built to order), that's another two or three 16 hour days between the hardware, software, network, and QA teams, since little can be done concurrently.