From the little I have heard, the charges against the cops appear to be overreaching by quite a bit. The prosecutor's husband is a city councilman. It is highly likely the charges are what they are due to politics of one kind or another.
The charges certainly seem excessive, but there's lots of speculation about the reasons for it:
She's playing politics to help her husband who's part of the local Baltimore leadership
She's trying to inflame the mob
She's trying to mollify the mob
She has political connections to the Gray family or their attorney
She wants her 15 minutes of fame
She wants to launch a wider political career
She's just plain incompetent
She's trying to get the case moved out of town so she doesn't get burned if it fails
She's wants a judge to reduce the charges rather than take the blame for doing it herself
She's under political pressure from the Baltimore mayor, or her husband, or the Justice Brothers, or Washington DC, or the media, etc