Yeah even though I agree with the COI being a large concern and potentially a justifiable reason for firing him (especially if coupled with other instances of him withholding key information from the board), it's clear that the non-profit board might have emotional reasons aside from the common good.

Even just the "you keep lying to us, bro" emotional motivation might be enough (not necessarily rational) motivation to fire; despite the person being otherwise qualified for the job, loved by employees and investors, etc.