Those craters are visible because there is no weather to erode them. You can see every impact that has happened in the last 4.46 billion years. Earth gets hit more than the moon but all the small asteroids burn up and the bigger ones get their craters eroded to nothing in a few million years or less. The actual rate of impacts is tiny and you’re worried about one hitting a very small spot that would have only hyper local consequences.
As others have said, the moon is already a high radiation zone. A melted down reactor would be worse but the contamination wouldn’t spread like on earth. Any release would be limited to the area directly around the reactor (likely within 1 mile at max) because there is no wind or rain to move contamination around. Not to mention that reactor meltdowns are actually impossible in some new designs and extraordinary difficult in others. Plus there is no weather to worry about. The only natural disaster that could happen is a direct strike from a meteor (also extremely unlikely) which can be protected against by building underground.
So no, you don’t have to worry about the moon becoming a radioactive hell scape.
We can’t understand their culture, but we can understand their reasoning. Assuming their technology doesn’t break physics and they evolved via natural selection then they will have had the same universal pressures shaping them that we did. Namely that one individual can’t know and do everything so at least some cooperation is necessary to reach space and they will use math and logic to solve technical problems.
Starting with the assumptions that they use math and aren’t suicidal you can eliminate a lot of the proposed fermi paradox solutions because they propose in some form or another that an advanced race that’s also stupid just appeared fully formed. Or the whole race suddenly gets a case of the stupids.
Given the size of the rock that killed the dinosaurs it seems pretty far fetched that aliens would have done that. It’s too small. They would have had to specifically wanted to kill most life but not all of it. When you’re talking about eliminating threats from interstellar distances you go with overkill. You hit somewhere hard enough to rip off the crust and make the planet molten again.
Now if you want to say aliens saw dinosaurs as a dead end path for evolution and hit the reset button that would at least make some sense.
Either they think they are the baddest guy around, which will eventually be wrong, or they worry about what others will do. Destroying a biosphere is not a quiet event. Anyone with the ability to do so also has the ability to monitor for that. So if you take out someone else you make yourself a target.
But why would evil aliens wait for intelligence to evolve and be a potential threat when they could just destroy every biosphere before life can produce intelligence?
Let’s assume there is some advanced civilization that doesn’t want competition and kills any aliens it finds. Would it make more sense for them to wait for an alien race to develop technology and be on the edge of being a threat before they take action, or would they just destroy the biosphere of any planet they find that could eventually evolve intelligence? My bet is they wouldn’t wait around for a threat to appear, they would prevent it from forming in the first place. With that in mind, we are on the verge of being able to detect if nearby exoplanets could support life. A much more advanced race should be able to do this for every star in a wide area around it, if not the entire galaxy.
Earth has had life for about 3.7 BILLION years. It should have been detectable for most of that. The Milky Way is about 100,000 light years across which means an advanced civilization anywhere in our galaxy should have known that earth supports life for basically its entire existence.
So we are left with three possibilities: Advanced aliens exist and don’t care Advanced aliens exist but are waiting for us to be a threat before doing anything Or advanced aliens don’t exist.
I find option two to be very unlikely.
This isn’t the only problem with dark forest theory though. If life is common enough that intelligence pops up everywhere and competition for resources ensues then no matter what kind of FTL travel you may or may not develop it is inevitable that you will eventually run into a civilization more advanced than you are. Unless you can instantly occupy the entire universe at once, someone somewhere will have been far enough away to develop more than you by the time you met then. In such a case you want to be seen as a nice neighbor, and not a locust, or you risk extermination.
As to your point of not being able to look for life across the galaxy from a single solar system, I think you vastly underestimate the power of technology. We already have plans for how to survey every star system in the galaxy. The telescopes required are just several orders of magnitude bigger than our current best. Making them would be an economics problem, not a physics or engineering problem. But if a race is at the point where they can destroy a biosphere from light years away they are necessarily at the point they can build those telescopes.
An RTG can’t leak. It doesn’t have liquid to leak out. It is an entirely solid device. You clearly need to learn a little more about how anything nuclear actually works before you try to say it’s a bad idea to use them.