There are certainly enough good questions specific to AWS to go around... enough that I managed to earn an amazon-web-services
golden dupe hammer gold tag badge on SO despite the fact that I have no affiliation with Amazon and have been answering questions on the topic for no better reason than the fact that I find much of AWS useful, well-engineered, and interesting.
Yes, it could potentially, arguably, drain some audience from Stack Overflow... but more often than not, the AWS questions on SO are not quite right for SO.
Many AWS questions -- including some of my most-upvoted answers, of all time -- like Why do we need private subnets in VPC? (+133) and What is the difference between an A Record Alias and CNAME in Route 53? (+46) are questions that were asked and answered on Stack Overflow -- but they're really not "programming" questions, so they really don't belong on Stack Overflow... and yet they're not obviously Server Fault material, either... and they are more advanced than what you would expect to find on Super User.
These questions could have been migrated here, if they hadn't been asked here initially. (Assuming "here" had been a thing, of course).
The point is well taken that "DevOps" might also be a logical place for such questions, but AWS really is its own ecosystem and a Stack Exchange community built around it makes sense: many of the questions that come to mind are indeed specific to AWS, not "the cloud" in general, and there are certainly communities with far narrower scopes than this.