Omaha resident here, albeit not involved in aviation nor airport ops. That weather, while it had been forecast to happen that afternoon, came up in a hurry. I had to drive across town at 1230, and the roads were wet but not slick. By 1400, there was almost 1/4" of ice on every exposed horizontal surface.
My guess — and that's all it is — is that conditions deteriorated quickly enough that the maintenance crews didn't have time to get ahead of the problem. If so, maybe they should have closed the airport before landing that flight, although all the nearby airports were having the same problem, so diverting the flight might not have been easy...I don't know. But I sure wouldn't call it pilot error.
Bottom line is that nobody was hurt, and it sounds like the aircraft didn't even take a whole lot of damage.
