Wait, I think there is a valid reason as to why nobody has been arrested yet. Snyder has no DA. She retired last month and we do not have a new DA. You need a DA to bring up the charges correct? Sounds like we need a lawyer to move to Snyder and take hold of the reins.
There are two points there. Firstly, a DA is an elected politician, usually they have an office with assistant DAs staffing it who do the actual prosecutions. The DA plays a managerial role. Snyder is a small county, but even so I expect there are more than one DA in the office. If the elected DA retired, one of the staffers would fill that position until the next election. I think it is improbable that any DA would retire when the case of their career was pending though, so you could read that as to mean that no charges are pending in Snyder.
The second point is that since the discovery of the body, the FBI has apparently been the goto agency for comment (even the Snyder sheriffs department directed reporters to talk to them in one news report). That implies that the FBI has claimed jurisdiction. Alternatively, the Snyder sheriff's department has recognized that they do not have the expertise or experience to conduct an investigation like this. If the FBI does have jurisdiction, then the case would be prosecuted in federal court by a US attorney/assistant attorney.
If they determine that the body was dumped in Snyder, but the crime took place in CC (for example), then the case would be sent back to that county for prosecution. Since the FBI is apparently still running the investigation I would guess that as far as they know, the crime did not happen in CC. Either that, or they just don't want Toombs doing the investigation.
In any event, because of the publicity associated with this case, a trial likely would not be held in any of the local towns, it would probably be in one of the neighbouring cities.