TL;DR: we saw a burst of energy (scientific name: luminous fast blue optical transient) that we previously thought only came from a star going supernova, but this burst came from the middle of nowhere in the sky and therefore was not caused by a star exploding. So now we know that these explosions (LFBOTs) aren't just made by stars.
Until a better theory comes along, I will assume we just witnessed our first warpcore breach. A moment of silence for the ship, and may her crew have gotten to the escape pods.
With a title like this, it's kind of disappointing that the answer is just "good infrastructure planning" and not something like "the land is cursed such that all who walk upon it shall rise again forever more."