I think there was more than 1 node when he launched it, if that was the case then anyone else was able to take control of the blockchain at that time.

Second thing, is the domain name bitcoin.org, how he used to purchase it ? Purhapse any anonymous payment method at that time like Liberty Reserve or ...

But at that time, why he would manage to keep him self anonymous with this revolutionary technology ? except if he didn't want that someone will make pressure on him in the futur to stop or limit it.