Reminds me of a "self-demotion" that worked out well: That of a certain Allan Vermeulen [0] who, by some accounts, was the chief architect of Amazon S3 [1], and by all accounts, an engineer extraordinaire. Vermeulen managed the Platform Services group when he joined [2], and later moved to a CTO role with focus on the then very nascent Web Services initiative [3], but eventually "demoted" himself to an "AWS Engineer" role to actually build key technological pieces that would underpin a lot of distributed systems at AWS [4]. Not bad at all.
[0] https://books.google.co.in/books?id=yG3PAK6ZOucC&pg=PT229
[1] https://perspectives.mvdirona.com/2016/03/a-decade-of-innova...
[2] https://archive.seattletimes.com/archive/?date=20040418&slug...
[3] https://web.archive.org/web/20091226191003/paulwallis.ulitze...
[4] https://www.youtube.com/watch?v=QVvFVwyElLY