David Hambling explains (in Swarm Troopers) the history of quadcopter drones:
A helicopter is necessarily a complex, delicate, and expensive piece of equipment. This is because steering involves changing the angle or pitch of the rotor blades, which needs an elaborate mechanical arrangement. The quadrotor has four sets of blades, and steers and maintains stability simply by speeding up or slowing down different rotors. Without modern electronics, it would be impossible; with them it is easy.
Modern multirotors date back to the late 1980s with the Gyrosaucer toy produced by Japanese company Keyence. However, modern developments tend to be traced back to US engineer Mike Dammarm, who developed his first battery-powered quadcopter in the early 90s. This was marketed by Spectrolutions Inc. as the Roswell Flyer in 1999 and later adapted into the Draganflyer, a range which is still going.
Multicopters multiplied, and the big breakthrough came in 2010 when Parrot produced their first AR.Drone. This was hailed as a fantastic toy: a helicopter sending back video via Wi-Fi which you control with an iPhone. The AR.Drone was a bestseller, and the world woke up to the potential of multicopters.
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Multirotors have a couple of major advantages over fixed-wings. For one thing, they can operate indoors, going through buildings, tunnels, and bunker complexes. And they give a more stable view than a moving fixed-wing.
Multis do have those advantages, no doubt, but a fixed-wing aircraft of similar weight can generally be propelled by ONE of the quad’s motors and stay aloft for over 4x the time. And fixed-wings generally handle adverse weather better than a multi. That adverse-weather advantage is even greater for a flying wing. And the same tech that keeps a multi stable can be used on FW.