Because in the 90's for example, your typical lithium ion battery would have been too heavy for an electric quadcopter. The electric motors for each of the quad

Because in the 90's for example, your typical lithium ion battery would have been too heavy for an electric quadcopter. The electric motors for each of the quadcopters fans also became very efficient recently (< 20 years). That is why this category of drones were not viable 30 years ago. Gas powered remote control flight has certainly been available for a long time, however commercial GPS for navigation and high bandwidth wireless connections and cameras for video feed certainly weren't available. These RC planes used to be a novelty, you'd fly within visual line of sight only. Now you can bomb targets 1000 km away with them with decent accuracy as shown in Ukraine - Russia war.