As other commenters and the article noted, when AWS was launched, it just provided simple, primitive building blocks like compute (EC2) and object storage (S3). At the time, AWS's value proposition was entirely around elasticity of infrastructure and its archenemy was data centers. In the process, they created a new market that came to be called Infrastructure as a Service.
Since then, AWS has gone up the stack steadily, adding infrastructure application services like RDS, ELB, etc. These infrastructure applications have made it easier and faster to deploy applications on AWS, but unlike pure infrastructure, they come with a degree of vendor lock-in. But developers didn't blink at all because it was so much more convenient than upgrading your own MySQL or setting up an HAProxy.
And now, AWS is squarely in the applications business. Last year, they announced Quicksight, signaling to the world that they are going to squeeze out business intelligence vendors. Few know that Amazon has Microsoft Outlook/Gmail for Work competitor called WorkMail. Slowly but surely, AWS is trying to swallow the entire enterprise software stack. I noticed that most people no longer describe AWS as "IaaS" but as "cloud infrastructure." I.e., their scope and market is expanding.
Key to this success is their strategic prescience and marketing execution, both for the developers and the suits. They knew what made developers happy (free/cheap to start, great API and documentation, scales well) and took the time to build solid infrastructure. For the suits, they created a clear vision of "old v. new" and used customers like Netflix to convey how the new world is going to run on AWS.
As a keen observer and practitioner of enterprise software marketing, AWS's rise to dominance is a textbook example.