Placements system deciphered?
Okay first of all, this is just a theory of how i assume the placements system works. I'm not too sure if this theory is accurate so you can downvote/upvote if you believe i'm wrong/right.
I believe your KDA has to do with where you are placed, that including your mmr and a bit of how many games you won but mostly your KDA. I'm assuming this because Riot's been trying to rid toxic players and the new placements system is made to melt you down until it becomes worst than even burning in hell forcing you to go crazy and pull out your hair. League does have its title for having toxic players and i'm pretty sure every league player hates this fact and Riot will do anything to remove these toxic players from the game.
And also other than all that gimmick, Riot is trying to make you play in pre-made teams, they're encouraging players to play with friends, because oddly by playing with friends players are statistically less toxic. I'm not much of a Brofresco fan but if you watch his newest video on Youtube about the new feature in the coming updates you can clearly see that riot is urging players to play with friends. Of course not entirely was it made just to help players become less toxic but it does make a lot of sense that it has an effect on imposing to reduce the toxicity in the game.
Although my theory may sound ridiculous even though we will never know, post down your theories too.