"Then, for no particularly good reason, this is combined with some smart contract / crypto coin scheme. Other than for PR purposes, it's not clear what the gain is."

Oh, it is entirely clear what it gains.

Cryto currency backed equity is just free money that you don't have to pay back if things go south.

There are basically zero protections for the "investors". Numerai could just walk away with the money and they'd probably get away with it.

Why wouldn't you turn down free money that the market is throwing at you?