As I read the article, he went off grid to show everyone else that it was a viable idea. Meanwhile, the island power grid did some pretty awesome things with solar cell parks and battery storage, rendering his pioneering efforts futile. To his credit, he seems fully aware of this.
The whole story thus boils down to a nice, illustrative all-other-things-equal experiment of how off-the-grid self sufficiency stacks up against a renewable energy power grid "done right". The latter winning by a large margin.
That being said, there are plenty of sunny places on Earth where the power grid is dysfunctional, or is hard to access. Those would be more obvious places for DIY solar panels.