Some Indians, seeing a horse being ridden for the first time, and having never ridden an animal in their lives, on first sight assumed the horse and rider was a single very weird animal.
We’ve had three Donkeys over the past 21 years, and still have one that is now 26 years old. I can tell you that I believe your theory is correct that the Donkey’s probably reacted to the unit of the scooter, and the person in fear, thus defensive mode. Most unfortunate.
The Donkeys we have, and had prior to losing them to old age were like BIG puppies. Gentle, loving creatures one would never think would do any harm whatsoever, but yes they are effective fighters when necessary so we have read. Fortunately we never had to see that side of them here at the ranch.