This situation seems pretty unusual, even for the DB. A regional express train should have many more stops than that. It sounds a bit like they switched the train to a direct connection to the final stop because they switched to the other side of the rhine (so you can't make any of the other planned stops anyway).
The major mistake here was not making the stop in Troisdorf. At the point where they missed that they should have planned the earliest usable stop for the passengers that needed to leave there.
I would also assume that there is no safe way for the conductor to halt at any earlier stop. A safe halt would need to be planned at a higher level.
