There are over a thousand breakout sessions at every reinvent every year. Some of the speakers are sales people, some are engineers, some are managers. There are L5 or junior engineers who give reinvent session talks. It's a fun gig, but it doesn't mean that the speaker is some top executive or anything like that.
Rich was in the sales org. His primary job was sales. Reinvent is a sales conference. Speaking at reinvent is a sales pitch. He was a salesperson. I'm not sure why you're so offended by that. Being a salesperson isn't bad, it's just an explanation for why engineers wouldn't have heard of him.
What do you think Solutions Architects and Developer Advocates (between the two groups who do most Re:invent sessions) are?
Hell, what do you think re:Invent is? It's a sales conference.
In any company you have two groups of people: Those that build the product, and those that sell it. Ultimately, solutions architects and developer advocates are there to help sell the product.
Of course Amazon is customer obsessed. And genuinely interested in ensuring customers have a good experience, and their technical needs are met - through education, support, and architectural guidance. But ultimately, that's what it is.