Earlier quoted context omitted.
Tesla's products allow for decentralized power. A Tesla solar panel feeds into a Tesla battery which powers your Tesla car and the rest of your house. That all works without Tesla building power plants or transmission lines.
Solar is generally moving away from decentralized consumer Solar to more industrial levels given the decreased maintenance burden. Why do we believe Tesla is on the right side of this?
In the new context a large solar installation connected to the grid is more cost effective if you need a grid for nighttime. The real question is whether batteries will make it so you don't need that. They're currently too expensive for that, but they're also declining in price. So if batteries get cheap enough that you can run your home from local panels and batteries without needing the grid, the cost of needing to keep the grid when you could otherwise not have it anymore makes the centralization lose its cost advantage.