always get trolls/smurf enemy right after getting 4-5 wins in a row

Why tf I always get trolls after some wins in a row? if no trolls, then the enemy team will be 2-3 diamond in last season. I am hardstuck low plat last season and started with silver1 this season. And I only had a 40+% win rate so how tf I get matched for diamond as well as have trolls in my team