I wonder why this game attract so much trolls?

Almost every day, I encounter trolls in my Ranked matches. Whether it is the enemy team or my own team.

What I count as trolls: People who simply tell they will troll, and go soft int / soft afk People who refuse to help in teamfights and say things as 'nop u dont deserve win' People who go to other lanes than their own, for example adc going top and leaving supp alone at botlane the entire match. People who afk in base since minute 5 and tell they won't play with a team like this People who flame others so much that they become tilted too People who keep going 1v4 in fights and know they will die, but they don't care People who refuse to place wards, 'we lose anyway so we dont need vision ggwp' People who already start trolling in champ select, ' i cant go mid? ok i go int and trol' People simply running it down under turret ( this is rare, but it happens ) People who troll pick in champ select to make you dodge and lose LP ( For example Soraka Jungle Cleanse Ghost) People who first time a champ in ranked. You know you will screw up probably. I see this as troll.

I wonder: WHY. Why would you spend time in a game, where you on purpose try to lose the match. Whát is the fun about it. I truly don't get it. Isn't it much more fun to stomp the enemy and win fights?