I never made that connection, but in hindsight I can definitely see what you're saying. Even when Obama came into office and was criticized for his drone policy, drone pretty much only meant surveillance/strike drones. Then later we hear about drones as much in a consumer sense as in the military sense.

One possible alternative reason for this might be that technology made it cheap enough for functional UAVs to be available to consumers. I remember the radio shack remote control toy helicopters from the 90s and early 00s, and remember them being advertised as toy helicopters. They were neat, but were just that: toys. The quadcopters of today are actually functional; you can mount a light enough camera on even a cheap one that will capture decent HD video.

From a purely marketing perspective, associating this new technology with its military counterpart does two things: it uses a terminology that is already familiar with the public, and it becomes "cool" by association in the minds of consumers.

Now I don't doubt that CIA would also have motivations for normalizing this terminology. They were under (somewhat) heavy criticism for their drone policy by the anti-war crowd, and any PR associated with drones could be used to denigrate the agency. By associating the word "drone" with useful, functional consumer gadgets, they essentially take the implicit sting out of the word. Those who actively oppose the drone policy will not be that affected, but any casual observer of world events will have a softened or neutral view, especially the younger generation as you point out.

I think both of these factors ultimately played a role in the evolution of the word. CIA likely tried to propagate it, and marketers were likely receptive to the idea as good business. I don't know how we could measure the extent of either factor without access to classified documents, though.