Will have to look up Anhalt again, but Grumpkow was both very competent (in Administration) and famously corrupt. As in, he took money from both the French and the Austrians, which was one reason why he was against the Hannover marriages for Fritz & Wilhelmine, though not the only one, and actively schemed against it. (His reports to the Austrians on the Prussian Royals still exist, which is how we know he missed a trick because he code-named FW "Jupiter" and Sophia Dorothea "Olympia" - should have been Philip and Olympias, Grumpkow!) Now I doubt he ever wanted any Prussian Royal dead, and Wilhelmine was biased due to him being co-responsible for making her life miserable for a good long while, but then again, she wasn't the only one to despise Grumpkow as a person - the Saxon amabassador loathed him as well and describes him as a vile character. (Again, he's the Prussian in the Maria Theresia series who after Prinz Eugen is of no more use to him leaves the old guy breaking down on the floor and ensures no footmen will enter the room to help Eugen.)

OTOH: he did mediate between Fritz and FW post-Katte. (He also ensured Fritz, who was deeply in debt, would get bribe money from the Austrian court, from the very same Eugen mentioned above. Not that this stopped Fritz invading later, but hey.) And he was extremely helpful to FW in restructuring Prussia and giving it a modern Administration. Presumably, he thought that nearly killing your successor is a really bad idea and not good for the state, and did recognize Fritz might make a good monarch?