Two things I haven't seen anyone mention that seem important:
1. For the villages that have now "made it" economically, there are countless others that haven't, that still live in one-room houses. What about them?
2. I think it's worthwhile pointing out that the product that he created, while popular and financially successful, is still used in the same settings charcoal is. And while carbonized briquettes produce less emissions that charcoal, there are still a non-negligible amount of particulates generated. By introducing a new source of this type of fuel he could be creating a local maxima that's still far from ideal. Additionally what are the effects of the type of repetitive labor these people are up to?
That said, it's wonderful to see someone lifted out of poverty. I hope millions more have the same chance.
(Do you get why some people are pushing back on your comment above? You can come up with this kind of stuff for anything. You can't eat an apple today without possibly furthering child labor, our world is too complex to try and turn every feel good story into a dig for downsides, because they will always exist. It is in no way "important" to do suss them out. And it's fine to discuss them, but you don't need to make it a reaction to the feel good story, you're allowed to just discuss these topics independently of the story)