Not that I disagree with what is said in this article or comments people have made, but the "marketing" of Agile began with the early certification effort in Scrum. Once there was a certification, lots of people wanted to pursue Scrum and to keep revenue coming through certification for trainers. After that companies started to want certified people (not knowing what that actually meant) in the same way they wanted various pre-Agile certifications. Once something starts to seem successful, the monetization grows quickly.