That would be a completely reasonable explanation and I could see that happening. But, there are some other details about the story that make me think there was more to it than that.
There were Sheriffs who reported seeing these fleets of drones. Sheriffs would normally try to calm hysteria rather than contribute to it, and it would be pretty hard to mistake a fleet of drones, not to mention they saw them moving in what they called a "search pattern". The numbers they were talking about were also higher than the number of traditional aircraft than can normally be seen at once, even near major airports with parallel runways in operation. If someone spots a few drones, I could see that being a mistake, but 17 flying in a search pattern? That person saw something exceptional no matter what it was.
Given the way that they worded this response, it seems like there was activity and that activity was found to be legal (ie. the operators had the appropriate 107 waivers to operate multiple drones and at night). It could have been your average joe, but that many drones makes it unlikely.
What else could it be? Lockheed Martin has a significant presence in Colorado and they hold both of these waivers that are necessary to operate multiple drones and at night (the FAA database is public and I looked in there for anyone who holds both waivers). Lockheed also has a small drone product in production that operates as a fleet with an extraordinary flight time and range using mesh networking:
Not to mention, Air Force Global Strike Command, "confirmed that it conducts counterdrone exercises" and it "oversees underground Minuteman silos spread across northeastern Colorado, southeastern Wyoming and western Nebraska, the area where the drones have been spotted nightly the past two weeks"
Unfortunately, we'll never know for sure -- it's impossible to prove something didn't happen. All they can do is not find them when they try, and that was over a month after the initial sightings. Of course, it's completely logical not to believe it unless there is definitive proof too.
Sounds to me like a case of one or two guys flying drones sometimes that turned into "What's that light in the sky?! It must be a drone!!"