The modern concept of genocide did not begin with the Holocaust; it started with the attempted extermination of the Armenians during the early years of World War I. The Promise tells the horrifying tale through the story of a love triangle (or perhaps quadrangle).
The foundation of the story is the devastation that war brings. Everyone in this story suffers from the war. Anna and Frantz’s parents (and many of the townspeople) grieve the loss of the young men killed in the war.
Theoretical mathematics may not seem a fertile ground for a movie, yet there have been some very popular and acclaimed films grounded in that discipline (A Beautiful Mind and The Imitation Game come to mind). It may seem even less likely to use that field to speak of the nature of faith.