There's enough out in the open to make a reasonable guess at the third thing. Sam was raising funds for a for-profit side gig uncontrolled by the OpenAI board which would develop TPU hardware to compete with NVIDIA. He was pitching autocratic regimes in the middle east, among others.

If the board had just found out about this, it would totally check all the boxes. Making something that could be destabilizing for the ecosystem or compete with OAI's partners, something which is arguably within scope of OAI itself yet he's raising funds as a venture he wholly controls while using time and possibly resources of OAI in the process (self-dealing?), etc.

It's enough of a gray area that all those things would be above board (hah!) if he had notified them and kept them in the loop, but a fireable offense if he hadn't.

It turned out he potentially zeroed a bunch of peoples' stock so the knives came out.