No pun intended - and it is about humans. We try to know, we try to figure stuff out. We try to make sense out of things. As does the main character here. He can't accept the loss of his brother - not without having anyone to blame. Now I am not saying he is wrong in his believes or that he is right in what he believes. I am saying it in general.
My father died of cancer - and I reckon many have lost loved ones to cancer. Coping with it - trying to figure out what made it grow in the first place .. there are things one can imagine. The same was true with the scenario with my father. I could (maybe rightfully) blame someone in that regard - it may have given me some closure. It might have muddled things more too though.
The movie here goes back and forth and leaves it up to you, if you are or how much you want to be invested. The ending seems to be clear - but still your sympathies and where they lie ... well may inform of how you like the movie overall.
