There isn't enough high elo players(dia+) to realisticaly influence lower elo, plats are trash, hardly distinguishable from golds, so they doesn't really count. Dia+ players will get to their elo pretty quickly, at least mmrwise.
Any proof that he really was challanger? He already lost one game, while he faced only one "smurf"(52% in 25 games) in enemy team.
Let's go through 10 last ranked games of yours, but first, let's clarify who smurf is. It's player who doesn't belong into elo he is playing at, which can be roughly guessed by their wr. Ok. So out of 90 players you met, 11 were "smurfs". But. 7 of them had wr in range from 46%-55% wr(one had only 13 ranks, so maybe bad luck), 3 were unranked(your chall smurf inclueded, one with 2 wins 2 losses and one with 2 wins) and one had 68% wr in 25 games.
So, at best, you met 5 smurf in 10 games(5% of players you played with might be smurfs), not sure how much influence could these have over players that play hundreds of games.