Spoiler: CS4 Ending (and explicit MAJOR CS3 ending spoiler) I don't believe it's laid out explicitly but removing the Vanders from their historic duty kept Matteus away from the Emperor and the possibility of his discovering what Eugent and Osborne were planning all along; That the two were working together rather than Osborne secretly working against Eugent's interests was one of the things that caught Olivier completely off-guard. It also allowed Osborne to create a replacement organization to fill that role. Given that the Great Twilight needed Ash's assassination attempt to happen (as a trigger for the Gral of Erebos to appear) replacing one extremely competent bodyguard who probably would have gone for Ash's head in a heartbeat with a group who could be directed to be less than fully diligent on the crucial day probably was a factor. That this also deprived Olivier of some of his support (and thus forced him to work harder at his own anti-Osborne efforts, making it less likely he'd act as a spanner in the works) was probably seen as an added bonus. As far as the status of the Vanders after the Great Twilight, they don't explicitly state that they were restored to their old position but Mueller is seen in the ending stills escorting Olivier and Alfin on one of their tours to reassure the populace which rather strongly implies that it happened.