Carmack was the programmer who wrote the core bits that made the game possible. He didn't engage with the popular press, and when he did engage in discussions with the media or with fans, it was at a very deep and technical level.

You may also think about it in terms of Wozniak and Jobs. Point being that Alan Kay was out there, engaging the press and talking about Smalltalk's big ideas (objects, messaging, computers as medium, how they relate to children, etc.). He was the frontman. Whereas Dan Ingalls deserves the bulk of the credit for actually writing Smalltalk.

Fun fact: Ingalls wrote early Smalltalk versions... in BASIC.