I don't understand

So what's wrong with people trolling, flaming or picking your champion on purpose then insulting you after ?

I mean it's worse than last season, every game you have somebody coming and speaking nonsense which will be the one feeding, then the next game you got someone flaming you because you don't ss enough or because they just find it funny to insult people and ruin the game, or you'll have someone AFK from the beginning (not including the people that have lags and disconnect because of it) and it will be a 4v5 forced

I just can't understand anymore what motivates people to do that