Two things spring to mind. One how, long had Radovid been conspiring with Nilfgaard to eliminate the Lodge, was he in Vizima to talk with Leuvaarden, whose family ousted and helped re-throne young Emhyr? Leuvaarden destroys the Order, whose presence in Temeria under DeAldersburg (and strengthened by mutants) might have given even the Black Ones pause. Was Radovid there also to co-ordinate a joint offensive on the lodge, and perhaps even lend aid to the Kingslayers who were at first targeting Redania's old enemy Kovir/Poviss?
Two, were the Lodge working at undermining and snapping up Aedirn, and if so for how long? If Stennis dies at Vergen Iorveth goes south into Aedirn to collect a large host of Scoiatael, but should the prince live then Iorveth goes east, to scrape up what he can from the Blue Mountains. This points to the Scoiatael being engaged in work to the south that becomes pointless upon Stennis' death, maybe the undermining and harrying of Demavend's nation. Maybe this is what has brought the formerly cunning old man to the brink of imbecility and alcoholism, a concerted guerilla campaign against him by scoiatael commandos and the manipulations of the Lodge, as well as a peasant revolt sapping his resources.
We know from Letho's assassination that the Kingslayer only escaped with the aid of Iorveth's commandos, but the old fox didn't know the Assassin when they first met outside Flotsam, so it was Sorceresses commanding his Scoiateal there. This all has the ring to me of a very long term and concerted attack on Aedirn from within, so that Saskia's Lodge ruled ascension can come about smoothly.