Well obviously no one knows... or very few people know (I still think that there are a couple original bitcoiners on this forum who are 99% sure that they know who Satoshi is).
Whats your favourite theory?
Mine is that it was John Nash

Please provide some proof for your theories. Would love to look into them!
One of the first tracks was an American of Japanese origin Dorian Satoshi Nakamoto. Everything would be right - and his professional name and professional experience - he worked on secret military projects as a programmer, and then he started working for financial institutions. For this he lived only a few streets from Hal Finney, who was the first to make bitcoin transactions.
However, the revelations of the American "Newsweek" have been overthrown, when the foundation of a true creator of Bitcoin put on the Internet entry: "I'm not Dorian Nakamoto" (although experts suspect that this entry is a hacker work). In addition, his network entries did not resemble the language used by a mysterious programmer from Japan.
So the eyes of the world turned to Finney - he was said to have used part of his "neighbor's" name as a pseudonym, he was first interested in cryptocurrency, so he had to be its creator. He denied these revelations. How was it really? We will not find out because the American died in 2014.