The first AWS service was SQS in 2002.
The wiki also says that AWS changed direction after a paper was written about reworking the retail compute infrastructure. It had a small section saying that they could sell excess compute as part of the rework.
After that paper came out they relaunched AWS in 2006 with S3, SQS and EC2.
Its difficult to find objective answers without being pitched by somebody on their company's own products and services.
But the forced login - why should one freely contribute knowledge if it is siloed by a company? - ads, frequent clickbait/opinion/irrelevant/crazy/advertisement-style answers and irrelevant notifications ruin the experience for me.