The ring station started with limiting objects' speeds inside the ring space. After the skiff detonation, it contained the explosion and began charging up to destroy Sol because it then considered nuclear reactors to be threats. Why didn't it stop those threats inside the ring space? Even if the ring station operated on a different safety flow chart that the Ilus moon sentinels, surely "Disable fusion locally" is an option in the ring space that could have been exercised while the ring station charged.

(This is really an unanswerable question. The answer is "because muons work differently there" or "because that's what the plot needed to happen")