Why are higher elo players the most toxic?

I was just playing a Normal game and i got paired up with 3 platinum and 1 gold player, i assumed all of them were premades but i wasn't sure until the game was over.

Anyways, this braum and vayne were duo bot (both of them platinum) and i decided to gank bot (i was playing rek'sai) i ended up getting a double kill and both of them immediately started flaming that i shouldve given them the kills even though vayne was close to death and braum had left the fight.

They continued to call me garbage because i didnt know how "important" it was for vayne to get kills, i roamed to bot lane a little while later and cleared some wards, the braum walked up to a ward and i ended up killing it, after i killed the ward braum started spamming chat with stuff like "go kill yourself %%%%%%" "you are fucking worthless"

After the game braum and vayne continued to trash talk and a few people on the enemy team and even another person on my team had started trash talking me, i had done nothing wrong and had carried our team to victory,

i'm not really insulted or upset, i'm just disappointed there are people like this in our community, i'm confused as to why or how someone can act like this and not get punished or anything. also how are these guys platinum when all they do is trash talk and get carried?

i have been playing this game for 5 years now and i have never experienced toxicity like this, ever... i was quite surprised

anyways, ignore the flaming... ** i guess my question is What makes people toxic and is it more common in higher elo players? **