Toxicity of higher ranked players...

I played a normals 5v5 game tonight with my friend, i'm unranked and she's bronze... She get's matched against a gold adc bottom lane.. I get matched mid against a platinum ranked zed.. I'm whooping his butt midlane and he get's sooo many ganks to help him.. so he ends up getting fed.. he becomes so toxic acting like the world is on his shoulders and like he did everything and talked so much crap.. like why be so toxic? He's platinum and i've noticed a majority of plat players i see talk major crap... why not help out newbies or be something to look upto? Why the hell would I even want to attempt climbing ranked if that's what people become? Feedback is welcome

TL;DR version:

high ranked kicks unranked butt and talks trash even though his team helps him the entire time

NOTE: This is not a QQ post..I'm just curious why so toxic, and also what's up with the pairing system ? that's all, feed back is welcome :)