Why am I playing against onyx's in placement match

Can someone please explain to me why I’m playing against such high players when I’m barley in my 4th placement match? 1st 2 were silver and golds then all the sudden onyx and high diamonds… I’m a crappy player so idk why this is. Thanks to all that respond!

because those first two games you won so they need to see where you stand because your are obviously above gold and silvers