Explicit details were never released because for some reason people seem to like watching Altman fall his way up the ladder.

Its crazy that you can be fired from that role and make sure everyone covers their tracks so you can go do it again elsewhere.

Only speculation:

"In 2019, Altman was asked to resign from Y Combinator after partners alleged he had put personal projects, including OpenAI, ahead of his duties as president, said people familiar with the matter."

https://www.wsj.com/tech/ai/sam-altman-openai-protected-by-s...

Regardless, this is another in a recent string of blows to YC's reputation for making people believe Sama moved on when in reality he was fired. What do you call making people believe something that's knowingly not true? Deception?

He didn't get fired: https://twitter.com/paulg/status/1796107666265108940