Whoever wrote this is an idiot. Here’s better explanation.
The black hole is 26,000 light years away. 300 years ago plus 26,000 years, a major supernova flare occured. It ejected massive clouds of gas. Those gases took 300 years to reach the vicinity of the black hole, and the effect the black hole had on that gas is just now reaching us. All the excitement happened back when humans were still duking it out with each other over who got the best mammoth steaks.