You're ignoring the fact that he spent a few years at Battery Ventures in between Netflix and AWS. Adrian is a well respected professional in his field, has been around for decades, and nobody holds any negative perceptions of him.
He wasn't hired by AWS because he migrated datacenters to the cloud. He was hired by AWS because he created this: https://netflix.github.io/ - Netflix's OSS, which has allowed them to attract so much great talent, was a direct result of Adrian's passionate open source advocacy. He's doing the same thing at AWS now, and has already accomplished great things like open sourcing all of the AWS documentation.
Disclaimer: work at AWS.