Lost two games in S1 at 76lp, sent me to S5?

So I was Gold 5 last season and played flex que. It placed me in Silver 1 (after the 10 games), which was quite nice. I won a few in a row and got to 76(ish)lp then lost two in a row, after the 2nd game it gave me a notification saying im being placed in Silver 5... Can someone explain why this happened? Thanks!