But he's not just Chairman, he's taking the title of Chief Scientist. It sounds more like moving into an IC role.
Jeff Dean became Chief Scientist when Demis took over his org.
It's still the typical title as a stepping stone towards something else (often outside).
The idea that “Chief Scientist” means anything more specific about what he does than “he’s a big shot who was in technology” is misguided.
A chief scientist can be super influential, or a guy who’s on the slow path to retirement but is keeping a paycheck to keep up appearances.