To be honest, I thought the way they approached Ravenloft was disappointing, as they apparently took into account Barovia as per Curse of Strahd, and not the setting as a whole.
My particular view of Kas is that he ended up being destroyed by Vecna in "Die, Vecna, Die!".
Among other problems that I particularly thought the adventure had, I ended up releasing a Companion on the DMs Guild, reformulating the plot and presenting suggestions regarding the settings and NPCs involved.