While it was far too late in coming, something was done.  He was convicted and sentenced to 10 years in prison, 5 other DIs were charged, the Battalion Commander was charged and 11 others were given NJP.  All 18 - their careers are over, 6 more face possible jail time and the other 11 most likely just hit terminal rank.  All of them will be out of the Marine Corps relatively soon. 
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As far as limiting "this power".  He didn't have this power, he abused his position and others allowed it to happen.
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Not to defend his actions at all, but name me another organization where an "employee" commits abuse / harassment and they go to jail for 10 years, co-workers that may have participated also face charges, the employee's boss's boss also gets charged and 11 others that knew about it get disciplined and fired.