It mentions fired in the context of 'disbanding' (as original article Huff Post quotes from mentions, I.e
Washington Post - 1st paragraph) and theres a difference between that and firing someone for misconduct. Some police departments are disbanded for financial reasons. Seeing that every single officer was out of a job for the department you're referring to seems like a blanket decision as opposed to evaluating each individual, including Black cops which I assume had a good record with black community. This statement in the original article supports that view where it states, "everyone was fired because city council wanted to start from scratch."
The article you posted is a good start but why is there no mention of misconduct from officer Wilson, specifically? Did he kill anyone or have any civil rights complaints against him? Why is he on Ferguson police force for 6 years with no complaints, except for one debatable one 6 years later?