How does the Ranked 5's matchmaking work?

Recently I joined a ranked 5's team with a couple of friends, all of us are individually ranked in Silver (the highest being a Silver 2) with one being Unranked this season. Throughout our promo games we were continuously placed against teams of high Gold's, Plat's and even the occasional Diamond solo queue players. We ended up being put into Bronze 4 with 3 out of 5 wins.

My question is, why were we placed in bronze 4, with a positive win ratio, when we were always against teams of higher tiered players? I understand that an individual player won't guarantee a team's ability to mesh well together and be a strong ranked 5's, but it's hard to deny that someone in Plat or Diamond brings a lot more skill, technique and experience to a game than a Silver player would. Since being placed in Bronze 4, our team has been playing against ranked 5's that are an entire tier above us.

I don't mean to sound like I'm whining, I just don't understand how the matchmaking system works for Ranked 5's and why we are always being matched against more experienced players instead of people on our own skill level. It's hard to learn anything when your team is constantly being blown out of the water.

Anyone with an explanation as to how the system works would be much appreciated.