I'm pretty confident it's not a personal scandal (or if it is, it's one that is truly monumental and that there hasn't even been a rumor of).
If it was a personal scandal, the messaging around his dismissal would have been very, very different. The messaging they gave makes it clear that whatever dirty deed he did, he did it to OpenAI itself.
What I was meaning to say in my comment was that the rumors and accusations relating to his sister, even if entirely true, are not monumental enough of a personal scandal to explain how the board behaved while firing him.
They'd probably still fire him, but would have done so in a very different way.
Maybe because it's not risking very much political capital. If he's wrong, and shuts up (rather than doubling down on it), nobody will remember what he said in two weeks.
Hell, some prominent tech people are often loudly wrong, and loudly double down on their wrong-ness, and still end up losing very little of their political capital in the long run.
Or maybe he's right. We don't know, we're all just reading tea leaves.
If he didn't know he wouldn't say anything. Why risk saying something when there's a very high chance that it's something like sexual misconduct or fraud.
If it was a personal scandal, the messaging around his dismissal would have been very, very different. The messaging they gave makes it clear that whatever dirty deed he did, he did it to OpenAI itself.