The drones were being used by the engineers on site who to monitor things and help plan for the intended demolition. It was more or less pure luck that one happened to be there at the time it happened.
Unfortunately for the viewing public it was facing the wrong way for the spectacle, but it'll probably be a fixture in engineering classrooms for years to come as a real world example of cable failure caught on video from up close.
Some neat things going on there regarding the cable. If I see it correctly, it looks like a few fibers snap at 0:02. Then nothing happens until 0:05. Stepping frame by frame with comma and period, it seems like a few more fibers snap, after which the strain is too much and the cable just explodes.
Cable number 2 goes in a more gradual way.
And on cable 3 there is a prominent wave before it falls to the ground.
I noticed this too. Even though it was facing the wrong way, I think engineering classes will still find it valuable to dissect the first and second order effects on these cables over time
During the press conference the NSF gave they indicated that the drone monitoring was continuous. They had a drone up to inspect the array every few hours. It was probably under drone observation for a significant fraction of the time.
> Or the drone wash was the straw that broke the observatory's back.
Technically not impossible, the drone was close enough to the cable that it was likely exerting some force, no matter how small, on them. There is certainly some chance that in that moment that force was all that was needed to push it past the breaking point.
That said obviously from a practical standpoint if it were that close the the edge then the next gust of wind would have done it in anyways.
Unfortunately for the viewing public it was facing the wrong way for the spectacle, but it'll probably be a fixture in engineering classrooms for years to come as a real world example of cable failure caught on video from up close.