Brian Anderson (AKA brson, who as it happens used to head up the Rust project) wrote a good piece back in 2017 called "The Minimally-nice Open Source Software Maintainer" which has tips to reduce burnout/disillusionment in junior contributors. It's less geared toward preventing burnout at the top, but still well worth a read, and there's no reason much of it couldn't be applied in reverse.
https://brson.github.io/2017/04/05/minimally-nice-maintainer