Having worked with several accident boards, let me offer this observation:
The board's primary purpose is to prevent any more accidents from occurring. If the initial findings produce facts that change the way we maintain, inspect or operate, they might be quickly disseminated to the users (a widget is failing, a nut is loostening up, etc). Sometimes, the inspections are proven unnecessary or prematurely required, but the risk of having repeats makes this burden very acceptable.
If the board sees a more routine cause, or simply none apparent, it will be much more deliberate, and will NEVER speculate (speculation means unfounded "I wonder if....." statements).
I have never seen a coverup in any way, on any board I have known. Those empty headed assertions otherwise are usually right up there with faked moon landings, Pentagon attacks by the USAF and grassy knoll gunmen, interesting speculation from ignorant people with too much time on their hands! Aside from the professionalism of those generally involved, most countries and Military services have shown the wisdom of having the board chair as an independent person, not beholding to the entity that operates the aircraft. At times, the NTSB in the States clashes with the FAA because of this, perhaps because the NTSB recommends sweeping (and expensive or perhaps impractical) solutions for isolated accident causes, and the FAA has to help determine the economic and practical impact of these recommendations.