Tolstoy is back to his pet theme of how historians totally don’t get it.
The basic argument here is this: if all you look at is events on the ground, as history does, then you’ll say that everything happens either because of random chance (which sets up a particular situation) or from personal genius (which sizes up the situation and finds a way to profit from it).
For Tolstoy, though, all of this is bunk. He’s out to prove that there is a higher power at work behind, or above, the scenes. So where we see genius, that’s actually a person totally predesigned to fit his given purpose, and where we see chance, that’s actually a predesigned bit of space-time meant to accommodate that purpose.