Some facts from early on indicate to me they knew this was bigger than two girls murdered in a small town in Indiana, but the SW's threw me for a loop. I'd wondered why they were going after locals, in the first week after the murders. I think what spooked LE is A) Whatever Libby recorded on her cell phone, and B) The brazen act of criminality which occurred, I think LE were shocked at how quickly it was over with.
MOO is they assumed it was a local. After all, even a lot of locals had no idea the bridge was there until the murders happened, which is common with old, out-of-the-way abandoned railroad and industrial properties. MOO is the perp was banking on this, and the fact that, as RL stated in an interview early on, nothing bad had ever happened around that bridge, before, and I believe him. The perp probably figured that LE would first go after locals, which put even further distance between him and the crime. Does he live within 60-100 miles? Maybe. He could live a lot further away from that, even.
As others have noted, we have not just one, but two victims. Not many abduction crimes perpetrated even by SK's involve two victims, and one must wonder if this is not the perp's first rodeo. I stumbled upon the Colonial Parkway murders case on here the other day, and man is it spooky, but the MO is somewhat similar. Two victims were murdered in each case, which certainly is rare.
In those cases, the perp went from sloppy in his methods, to more organized and slick in his methods. Hate to say it, but MOO is the perp in this case in Delphi is experienced, and that is what really got to LE after the first several days, as in they knew it had to be an outsider, and a targeted set of murders.
By "targeted" I mean this is a SK who stalks his prey and goes after vulnerable women, perhaps all of them juveniles. The perp could have researched the bridge and the area around it, online, for months, or perhaps he has a list of kill spots he's researched. Perp visits, could be wearing his regular street clothes or whatever, recons the area, sees how busy it seems. MOO is he knew Delphi schools had the day off, and that was one of several factors which led to the murders, and another big one would have been the weather.
We haven't had even a PC in several weeks, now. I think LE knows it's a SK, perhaps one that has struck several times beforehand.