Who’s surprised? They can’t afford to run on their biggest competitor’s platform.
ps: given that Amazon Video is available for all prime members, we can’t compare total number of subscribers. Hours of videos watched per day might be a better number to look at.
It would be an enormous risk for any cloud provider to attempt to degrade the use of their platform or snoop on how it's used by a company who is a competitor in another area, be it streaming or code management.