The bitter legal fight between Elon Musk ⁠and the leadingAIe firm, OpenAI, led by Sam Altman, may come down ⁠to a few pages in one executive’s personal diary.

“This is the only chance we have to get out from Elon,” wrote Greg Brockman, OpenAI’s president and a co-founder, in the autumn of 2017. “Is he the ‘glorious leader’ that I would pick?”

Brockman’s diary entry is part of the thousands of pages of internal documents revealed in court since Musk, one of the original co-founders of OpenAI,...