I don't think there's any evidence they are working at a snail's pace. LE has zero incentive to drag things out unnecessarily. The sheriff is an elected official. And he knows that.
The thing is, having a possible suspect in jail allows them to properly investigate and prepare an iron clad case for prosecution. It gives them the luxury not of moving at a snail's pace but of not having to rush, which could compromise the investigation.
We are curious. We are upset. We want justice. We want resolution. But real life isn't a tv show. It's not wrapped up in a few hours or days. And nowadays, with our CSI culture and juries that do things like let casey anthony get off scott free, they are more reluctant to take cases to a jury unless they have everything they think they need.
We are not LE and we're aren't in the middle of this investigation. But I guarantee they are working around the clock and are much more vested in this case than we can ever be. I feel defensive for LE at times in these cases. In this one for sure, knowing they saw the bodies. They saw the evidence, the video. They may have heard the girl's last words or screams. They have to live with that. I have no doubt they are dogged and determined more than anyone to get justice for those little girls.
Occasionally there are investigators and DA's who don't do what they should. I think that's more rare. And until we get info that shows they are not doing what they're supposed to do, ignoring leads, etc., we just have to be patient and let them do their jobs.
