Base on the responses others have given and your reaction to them, I'd say there is a bit of defensiveness in there. I don't know your friend personally so take what I say with a grain of salt but smarts (aka the genius) does not make a brilliant entrepreneur. Someone else said he's more of a employee #1 than a founder and I tend to agree base on how you've describe him even if he is the kind of person who refuses to be employee #1 of which there is nothing wrong with that. You can learn A LOT being an early stage employee rather than always having the narrow mindset of having make the leap immediately and doing it yourself.

In regards to why I think he isn't suited as an entrepreneur (at this time; important to note this distinction for now) is because he has reservations and requires someone like you to push him to make the leap. Entrepreneurs are driven to make things happen, not be convinced. That behavior will only make things more difficult if he doesn't have the conviction to try himself now, regardless of what anyone says (good or bad). And there are folks out there that no amount of convincing would they ever change. Not saying your friend is like that but as others have said, it's coming out as a red flag.

In response to another response you made, social proof is not like a letter of recommendation. It's not his professors that will grant him social proof. Social proof is validation from people that matter to the VC's in their social circle.