I think it is more likely that in the DV their were other supernatural players working in the background. If you want to use the history of that time I would point to the rise of the faction known as the Young Turks starting around 1908. You might ask why I think the rise of those leaders is important. Remember that Bob told Harry that Kemmler was responsible for engineering WW1. The Young Turks helped bring Turkey closer to Germany and eventually to join the war on the side of the Central Powers in 1914.
So I suspect Kemmler was involved; possibly directly or through the use of catspaws, in the attempted assassination of the Sultan. He wanted to bring down the already tottering Ottoman Empire. I doubt that either Ebenezer or Kinkaid was the bomb thrower. In fact, my guess is that they were nominally working together to oppose Kemmler or his agents. Only they would have had different reasons for doing so and different employers. Obviously, Kincade is not part of the White Council, but just as Harry has worked with Marcone, Mr Hendricks, Ms. Gard and Lara Raith; in his time Ebenezer has formed temporary alliances with people and not people who weren't always friendly towards him or the White Council in general.
I think Ebenezer's anger towards Kincade is not based on them being on opposite sides in 1905, but that they were on the same side and after they accomplished their mutual mission; or perhaps in the course of that mission, Kinkade fulfilled a second contract that undermined or betrayed everything Ebenezer had been working towards. And whatever Kincade did, I bet it was really nasty, or led to something that could be described that way. Eb's anger felt to me like it came from someone who was personally betrayed by an ally, not anger at an old enemy. So in the end, Kemmler's ambitions were served.