Presumably, at least based on part of what O'Keefe was saying in that video that was released, the instigating incident "seems" like it may have been when he had finally fired a board member who kept butting heads over regarding how he ought to tackle fundraising efforts.

The details were a little vague, but the impression I got was that the board member just wouldn't stop making a serial case over it and O'Keefe got fed up. And then after firing that board member, the rest of the board just lost it and went after O'Keefe entirely.

It's not clear what ultimately had been the prevailing agenda or motive for the board here, but my own suspicion is either they were getting paranoid about potential legal fees or they were just getting straight up greedy after the success of the Pfizer story.