“Thou shalt boil water before drinking it” would probably have saved a staggering number of lives. That and a handwashing commandment together would’ve been a home run for pre-industrial survival rates. “Thou shalt not trust a fearmonger” would also be a good, if perhaps self-defeating commandment.

Yup, RTGs exist, but they’re impractical for most terrestrial use cases. The problem is that any isotope that’s energetic enough to generate meaningful amounts of energy is also going to be somewhere between quite dangerous and insanely dangerous if the container is breached. And unless there are very strong protocols in place for handling the RTG, on a long enough timeline, there’s basically guaranteed to be a nuclear accident.