the case's judgment did not mention when Bouchard was sacked or why
Unfortunately, without the why, it's impossible to really see who's at fault here. There must have been some serious friction, as he wasn't a lowly minion, and he went over to FB HQ on a self promotion visit which resulted in him being employed by them. Did he benefit from the acquisition through share ownership? Or was he just a talented guy whose employer changed due to acquisition and he couldn't fit in with the corporate worship demanded by the big new boss?
Still, without information it's best to assume that he found that working for the cult of zuck sucked.