B03 Series == lower elo team?

Hey, I play on the BR server but I figured this issue would be the same for every region.

I was in plat5 season 4 and after stopping playing for a while and losing 5 of my bo10 I fell in Silver 3. Now I'm at Gold 4 climbing. One thing I noticed though, best of 3 series are WAY HARDER to win than regular games. I don't come here to cry, just to understand if Riot has a logic to it because it cannot be pure coincidece. Just now I have won 9 out of 10 games with no issue and on my first series game I'm last pick (which is ok) and there's a player feeding intencionally.

I know I will climb back to plat eventually because I'm playing well, but is this a conscius decision to make low elo/bad attitude players to fell in your team? It took me 4 bo3 to get me out of gold 5, and I'm noticing this at every series again and again.

Thanks,

Dom