It's the application of the technology that has gained popularity. Advances in electronics allowed the production of cheap lightweight flight controllers, accelerometers, global positioning systems and cameras. This resulted in a rapid proliferation of small, cheap consumer quadcopters and other multi-rotor designs. The video and image applications are obvious. What I didn't see coming was FPV. This is the fastest growing segment of the hobby. It's as close as you will ever come to flying, but with your feet firmly planted on the ground.