In my opinion the greatest evidence that tells me the satoshi was a single person and not a team is that his identity is still a secret, it is very difficult to keep a secret when there are many people involved, someone will always talk and will reveal the secret, and that has not happened, his identity is still a secret which means that most likely the only one that knows the secret is himself in that is why he can keep it that way.
But he must've come in contact with somebody?
Somebody knows him, right?
If he lives on planet Earth than he made some social connections.
He shared some of his ideas with some co-worker or something.
No, It's more likely that that person doesn't exist and that some big organization is behind it all.
When something desn't exist it's easy to keep it "hidden".