Number 1 is huge, it's also the primary driver of the shift from "model planes" to quadcopter drones with enormous capabilities. The crucial parts were brushless motors and ESCs. The Chinese scale brought the pricing down from ~3-4 figures to under 3 figures which was a watershed moment for hobbyist and commercial use cases.
The other big one for drones was sensors and the processing to run them. Trivially small cheap gyro position sensors, accelerometers, GPS, pressure sensors, etc... needed to exist since quadcopters are more or less incapable of flying without a computer in the loop.
