Plan9 was a network operating system, and with a focus on concurrency a new language Alef was designed with coroutines based on CSP formalism (Hoare's communicating sequential processes). That was redesigned in Limbo language on Dis garbage collected virtual machine in plan9's replacement Inferno OS. Go's goroutines and other choices are next incarnation of these ideas designed by many the same Bell Labs people, not just one incidental lead. Shopping for a light compiler to bootstrap from is peripheral to the design story here.

Fuchsia doesn't share as much of the story but does pick up where in Dante's Inferno the original Unix people tried to abandon the root user to redeem themselves almost 30 years ago. Combined with capability based model last seen deployed in the wild with OS/400 and Burroughs machines before that, it would be the first truly new OS in decades.

Not only one developer. Rob Pike, Ken Thompson and Russ Cox were fundamental in Plan 9. The early versions of Go's standard library were very based on ideas taken from Plan 9 and Inferno, and even the compilers were very similar.

Although it would be wrong to consider Go as a derived product of Plan 9, I think it is right to call it its intellectual successor (although not the only one).