It has always seemed pretty certain to me
Discussion
Or, it's the Elon Musk Troll theory and he's really a mixture of conglomerates.
Personally I think he's really just letting people do what they want with Bitcoin to see what they make of it and he (or she) is living peacefully in full anonymity.
I’m not sure a human mind could create something as monumental as bitcoin then go on living peacefully