There are very few situations in which a person who claims to be a previously anonymous individual could prove their bona fides without a shadow of a doubt.

And this is one of those situations. There are multiple ways that the real Satoshi could prove their identity, but somehow, Craig Wright has either lost of of them, or they're locked up in some strange escrow with a super-secret board of lawyers or some such nonsense.

Occam's Razor. If ever there was a good application of the principle, it's here.

Also, Craig Wright doesn't have the technical understanding to have written the Bitcoin implementation. Listen to him speak. If you're honest with yourself, and if you code, you'll realize that he's likely never written much running code at all, much less a full implementation of a complex cryptographic and network protocol.

But these are the kinds of guys who unfortunately make it past interviews on the strength of their "dazzle'em with bullshit" approach to interviewing, and that have caused the current situation where most of us have to spend months reviewing our DS and algorithms notes before new interviews.