Why is this worth an S?

I had a ok game. I was not amazing, had one of the highest death counts for the team and lowest kill participation. I only helped get 1 dragon.

Why on earth did i earn an S with shen this game. It does not make sense.

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2144058637/38521493?tab=stats