Where did all these trolls come from?

Banning phase, our ADC chooses Varus. Our mid laner bans him without realizing, ADC goes all buttthurt claims hes going ADC Lux. I said support me, ill just go Jhin and you can do AP Lux. So we get in game from there he proceeds to go mid lane and purposely screw over our Ekko for his CS while also pursposly giving the enemy Kartus First Blood followed by 3 free kills. From there he tries to play the victim saying im the troll because i went Jhin and not as an actual support to support him and his ADC Lux. (He didn't even ATTEMPT to build ADC, he went straight AP from the start). This is why League is such a shitty game, its because of idiots like this kid, and the failure of a report system Riot has, allowing players to vote of their innocent or not. Because there's more trolls like that Lux in the game, than there are of people who play the game the way its mean to be played. So at the end of the day, you get muted for calling a troll a dumb ass. But the troll gets away free, nothing happens so he continues to go on purposely feeding/throwing games when his champion is banned.

We never had this many trolls in Seasons 1 - 3, where the hell did they all come from. And what is Riot actually going to do to get rid of them, because it seems their a lot more harsh on someone for calling a troll "Idiot/Dumb Ass" or some other form of name calling that isn't even overly offensive. But they seem to be O.K with players purposely throwing games and costing people their LP/Placements.

Only permanent fix i can see if Riot gets off their asses and handles the report system themselves and remove the whole voting system on reports to see if someones guilty or not, it's not working.