That makes sense if the businesses are unrelated, but that's not the case here. Batteries are critical to both Tesla's cars and energy storage products. Even before the Powerwall announcement, a lot of people called Tesla a battery company that just happened to sell cars.

Tesla has always been a bet on batteries. And if you're going to bet on batteries, why not expand that bet?

Regarding "gobs of cash," Tesla would be profitable now if it weren't pouring money into future expansion. The Model S sells well (given Tesla's size) and has high prices and margins. But that money (and more) is being put into design and production of a new model, and a gigantic battery factory.

I don't think Jobs is a good comparison to Musk. Jobs's recipe for success was to take products that existed and were popular in a niche, and refine them so that they appealed to a wider audience. The Apple II was a friendlier PC (used in the generic sense, not "IBM PC compatible," of course) with mass-market appeal, the Macintosh took existing GUIs and refined them to the limit, the iPod did nothing that existing MP3 players didn't do, but was made to have far greater appeal, and on and on.

Musk, on the other hand, is pushing the envelope. First electric car with a long range. First electric car capable of long-distance travel. First electric car that can compete with gas cars on its own merits. First reusable rocket (still trying).

If they were in the same market (and if Jobs were still alive), Musk's companies and products are the sort of ones Jobs would have been appropriating and refining a few years down the line once the concept is proven and demand is demonstrated.