8 Wins 2 Losses placed in bronze 5??

Last season i ended with Bronze 1 rank, once this season started i played my 10 placement games, winning 8/10 of them, in the 8/10 that i won i got two S grades, two A grades, three B grades and one C grade, and as for the games that i lost i got a B and a C, these seem to be pretty decent scores in my head, yet after i finished my last placement game where i went 15/8/3, i still got placed in Bronze 5? There shouldn't be any way that i get placed 4 divisions below where i was last season when i didn't even do that bad in my placements and in my personal opinion did actually pretty well.. i don't get how it's fair that you can do that well and still get placed in the worst division in the entire game