The article is being pretty hyperbolic. There’s no mystery here, this is just something which happens if you put two different metals together. It’s nothing more or less than a crude battery, just like the ancestors of the AA battery the article kept harping on about.
This discovery could be important for people studying the climate on very early Earth, people studying early life, and the ecology of the deep sea today.
That last one is particularly troubling, though. If this is widespread, then this might be a major source of what little oxygen is down there. If so, then taking those nodules away (like a lot of people are keen to do, since some of the metals they’re made of are valuable) could destroy an entire ecosystem.