Not only Amazon, it seems to be the case with other big tech companies:
- At Apple, this was famously 100% the case under Jobs. Under Tim Cook the company still very much seems cohesive on a single vision, is very, very focused in its products and from the outside it does look like upper-leadership takes credit for and oversees most things.
- Facebook still has Zuckerberg, which built the original product. Last I heard he was reorganizing the company so that "the heads of individual products, including WhatsApp, Instagram, and others, would report directly to him" [1].
[1]: https://www.buzzfeednews.com/article/ryanmac/facebook-chris