Politics. Switzerland does not want trucks on the road, so they load them on a train in Italy and unload them in Germany. Otherwise, nobody would bother, as it is about the worst system you can think of.
kof ola: Hello, small correction: Switzerland has nothing to do with the Brenner because it is Austria that wants to relieve the congestion-plagued Brenner motorway from the truck. And Wörgl is a town in Austria, where the train ends ...