A better way to phrase it might be...why oxygen instead of Sulfur or Selenium? Because those are both in the same column on the Periodic Table, they have the same number of valence electrons and therefore can form double-bonds easily. However, the obvious answer comes to mind at the same time: they're both solid at room temperature. So...maybe...in a higher temperature environment, it might be possible for life to selectively choose gaseous Sulfur over Oxygen. But that's not how things work on Earth (most of the time)

There are laws preventing spreading life to other worlds (at least for the time being)

I did not know that...cool

In that case, it's probably a gas plant, and...depending on its supply and whether or not anything has gone wrong, those can (generally) keep going for years without intervention. On the other hand, no supply = no power AND anything goes wrong = no power

So...it's probably not the plant operators leaving that caused the outage, especially since the grid is hyper-connected. It's probably a lack of fuel supply, from the refineries abandoning their posts...at least, if it's based in reality

Yes, and it depends. Is it a gas plant, a coal plant, a solar plant, a hydro plant, a nuclear plant? A plant of near-future design other than those I asked about?

We aren't even sure that the orbit of Dimorphos has changed, yet (observationally). We won't know if Didymos' orbit has changed until we can assess the impact on Dimorphos, but all of our theories say that both orbits should be different now.