apart from noise any annoyance, there is always a risk of aircraft falling out of the sky. They can fall out of the sky intact (loss of power) or in pieces (structural failure).
Normally both fixed wing airplanes like I fly, and rotorcraft (helicopters etc.) that lose power remain under control and can glide forward to a safe (more or less) landing, if they have enough altitude. We train on how to trade altitude for horizontal glide in such situations.
However some things cause aircraft to break up in flight, and then the pieces are scattered snd fall to earth according to the laws of physics. One example is a helicopter losing the rotor when it hits power lines.
there were two safety problems with that low level flyover.
First is that it was too low to allow for autorotation to a safe landing in case of loss of power (engine or transmission failures are not uncommon in helicopters). Those birds would’ve come down into the crowd if they suffered engine failure at the wrong time. Not good.
Second is that there are suggestions that cables were strung across the top of the stadium, and the helicopters flew under them. That is very unsafe if true, as they are not readily seen and avoided. More generally there are questions about whether flight planning considered possible obstructions within the stadium bowl. With fly by wire aerial TV cameras and movable roofs and netting’s and such that is a serious risk to ignore. Consequence of a cable impact would almost certainly put a helicopter into the crowd, possibly also stray rotor blades. Or worse, send one helicopter into another and then both into the crowd.
that stunt could have killed hundreds of people, maybe more if a real worst case scenario ensued.
it would be fun to watch the investigation but it will probably be hushed up.
My house is close to Davison Army Airfield at Fort Belvoir and we are frequently buzzed by low flying copters. Just a fact of life. They are not nearly as numerous or annoying as the commercial jets from Reagan National which used to be routed down the Potomac, but are now sent over heavily populated areas.
As for the flyover... 'eh if i was there, i would thought it was pretty cool to see that...