S Rank only for afkers or what?

Just won a game where the adc afked for 8 minutes. I won lane as nami and never died my team crushed except for the adc and he got an S rank despite having the most deaths, low cs, and being only level 10 when most were 14. Three people got an S rank but not me? I healed for more and deal more dps than any player the opposite team and most of mine. Wtf is deserving of S rank? Should I play 1v5 and be the only player to get any stats? Or afk for S rank because that works?