That’s a very good question… One would think that would have had to start showing signs of cracking before it let go. I’m not sure how often parks do in depth inspections like that but you would think someone should have caught it before it let go.
Reality is that no one was likely in any danger because the neighbouring supports would still be enough to handle it (in the video you can see very little movement) for a while but I’m still really surprised to see it get to that point.