I think a large part is that they’re inherently safer with four smaller propellers rather than one big one. So suddenly applications where you’d need a helicopt

I think a large part is that they’re inherently safer with four smaller propellers rather than one big one. So suddenly applications where you’d need a helicopter are accessible to people with less training and skill. Particularly with the robust flying assists and mechanical simplicity. Then they also turn out to be a readily accessible tinkering hobby very suited to flying around in areas people have nearby. The whole FPV and racing scenes bought in a demographic shift compared with helicopters and fixed wing. Quads are also fantastically agile so quite a different experience to anything else.