For Nvidia's part they're just giving money to one of their largest customers. They make money back even if they "lose" the bet

It's like government XX giving "help" or "grants" to countries at war so they can purchase weapons from XX.

Selling Shovels is quite lucrative whether there is an actual mining business or just a gold rush.

At one point Jensen Huang will be out (retired or forced by staginating sales) and can definitely look back on a very successful career. That much is certain.