[GeneralMayhem]

Slow oxidation underwater isn't useful for anything, though. You can't use it to do work without a lot of additional technology to capture energy over long time periods.

Set aside what we know about human technological progress. You need some energy source to be the base of your technology pyramid, and it needs a few properties: it needs to be naturally occurring so that you can discover it by accident; it needs to be controllable or predictable enough that you can use it selectively; and it needs to be fast/intense enough that you can transform materials without massive time investment. What do you pick? On land, you have fire, flowing water, and, at a stretch, the muscles of large herbivores. Underwater, you have... ???

Also, that's not what "anthropic principle" means.