A lot of other theories don't match because the board was in an extreme hurry to get him out (voting him out in the middle of the night, not even waiting for markets to close to announce it), must have proof of serious misconduct and the need to immediately distance themselves from Sam (otherwise the language would not be as bridge-burning as it is) and a major financial or technical failure seems unlikely, since the CFO remains and the CTO was even promoted to interim CEO - they seem to be trusted, still, so it must have been something Sam did on his own.
Leaking/Selling the full models matches, as this would violate OpenAIs non-profit terms, would be something Sam could do without the C-Suite being implicated and (given the data contained in the training set) might even be legal hot water, justifying this drastic reaction and immediate distancing.
With this apparent rush, I'd habour the guess that the situation just happened to unfold on a Friday and wasn't planned as such.
https://learn.microsoft.com/en-us/legal/cognitive-services/o...
I get that this looks like a strange coincidence, but major shareholders just had minutes of warning and they released the news before market close, sending Microsofts stock crashing down. Had they had the time to wait until Friday, they would have had 30 more minutes. So unless they had some fun with shorts, this doesn't look like a planned out action at all.