It's not as insane as it looks. After a few hours on an fpv drone you can easily fly like you see here no issues. Look up some of the pros flying around tight spaces on Youtube, now those guys are insane.

The bigger problem is that flying over people like this is a big no-no, and completely illegal in most parts of the world. Even the best pilot in the world can have a faulty prop and suddenly plummet down into the crowd. And while racing FPV drones like the one that is probably being used here aren't very heavy, they'll still clock in at 6-700 grams with camera, which could do some real damage if you hit someone's face at 100km/h