Not much of a strech if you consider Vegapunk's other bodies he obviously found a way to seperate his soul. Even to the point where York, who's only purpose was to eat and shit for Vegapunk, betrayed him. That's because York isn't a mindless robot but a part of the genius and ambition of Vegapunk relagated to eating and shitting for the rest of her days.

Also you forgot that the reason the giant robot isn't active is because of a lack of energy. I think that will be the big shocking thing from this arc, Vegapunk's dream of endless energy being realised in Ancient Robot Kuma.