Sam Altman spoke at an APEC panel on behalf of OpenAI literally yesterday: https://twitter.com/LondonBreed/status/1725318771454456208
https://twitter.com/phuckfilosophy/status/163570439893983232...
... and he was 13. Which, yes, is a very bad thing, but unless the company investigated that claim (e.g., to assess potential PR fallout) and there was some significant deception by Altman against the board in the context of that investigation, its not something that would get him fired with the explanation OpenAI has provided.
(OTOH, the accusation and its potential PR impact could be a factor that weighed into how the board handled an unrelated problem with Altman—it certainly isn't helpful to him.)