If the domain wasn't registered by Satoshi then most likely it was registered by Sirius - (Martti Malmi). Likely you will fund few more information here.

We can just assume someone from both of them registered the domain, but of course, most probably they had used the latest technology to hide their real identity. And based on that, I can say Bitcoin is truly decentralized since even it doesn't have an official website.

No one could give you exact answers about Satoshi's motives, better search Google and get some ideas.